The MENU: Wilted cucumbers vinaigrette Poached or steam-baked Whole salmon Hollandaise or mousseline sauce Green beans and Jerusalem artichokes Steamed new potatoes Chocolate Roll Leontine For leftovers Puffed salmon pie

IT IS ONE of life's satisfactions that a whole cooked salmon is pleasing to the eye, delicious to the taste buds and simple to prepare. This most wonderful fish has just come on the market fresh, and on schedule, along with peonies, fox-glove and clematis, for Memorial Day.

In today's almost-summer menu, the salmon is served warm with a hollandaise or a mousseline sauce (a hollandaise lightened with whipped cream), steamed rather than boiled new potatoes (no sog) and, for color, crunch and a bit of variety, cut green beans parboiled and stir-fried in butter with thinly sliced Jerusalem artichokes. Peas are traditional but I am tired of them. Snow peas, which I did a test run on, have too strong a flavor for the salmon.

The meal begins lightly with dilled cucumbers, whose flavor is brought up by being wilted. These would have accompanied the salmon had it been served cold with mayonnaise. Here it prepares the palate for wonderul things to come. The cucumbers need a little French bread and butter.

Desert is Dione Lucas's feathery Chocolate Roll Leontine, which mercifully has nothing in common with the fashionable chocolate glops that eradicate all memory of the rest of the meal.

Most of this meal can be prepared in advance. The cooking liquid for the salmon can be made at least a day before and refrigerated until needed. The cucumbers can be wilted and seasoned the morning of the party. The green beans can be cleaned, cut and parboiled the day before. The potatoes can be scrubbed any time and put on to steam 35 minutes before the salmon is to be served. The Jerusalem artichokes can be peeled and sliced in the morning and set in a bowl of water with lemon or vinegar until they are rinsed, dried and cooked. The cooking, which takes 2 minutes, can be done just before the salmon is served. The chocolate roll can be made the night before or the morning of the party. For the salmon's cooking, count backwards from the time you plan to sit down. Skin the salmon just before you start the first course, arrange it on a platter, cover with a tent of foil and place it in a 250-degree oven to keep warm. Then decorate the platter before the salmon is served.

I either poach salmon in a court bouillon or steam bake it with an aromatic mixture in foil. One advantage of the second mixture, besides the moist and flavorful fish it produces, is that it can be done without having to invest in a pricey fish poacher (and the cheap ones are too thin and not good). The salmon can be fitted into a large shallow roasting pan or even a jelly roll pan, if necessary on the diagonal.

In order to poach a whole salmon, you need a long, narrow, deep pot with a lid. An old-fashioned covered turkey roaster will do. But the best is an aluminum or tinned steel fish poacher, equipped with a rack that conveniently lifts the fish out of its cooking liquid.

When poaching salmon, it is a good idea to wrap the fish in cheesecloth, leaving enough of the cloth at both ends to use as handles. This makes it easier to manipulate the cooked fish, whose skin needs peeling and which must be placed on a platter. The cheesecloth can be washed, rinsed thoroughly and reused. The foil can be made to serve the same function for the steam-baked recipe.

A headless salmon that weighs 4 1/2 to 5 pounds (this is considered small for a salmon) is ample for eight, plus some leftovers. It is, however, often easier to find a larger fish, and this has its advantages. Served cold the next day, it would make a lovely formal meal for family and a few friends. A couple of cups of salmon will make a cold mousse. One cup, along with a pound of shrimp, will make a terrific puffed salmon pie, which I adapted from Henri-Paul Pelleprat's "Modern French Culinary Art." This serves six and is good for another party.

Salmon is not an economical item, but to me it is a justifiable if occasional indulgence because it goes far and it does tell guests they are special. Salmon can be had for less than the price of a handful of truffles, but only if you shop selectively -- last week, fresh salmon ranged from $5.25 to $9.99 a pound.

At Claxton's, a wholesale fish outlet at 240 E Street SW, which also sells retail, fresh salmon costs $5.25 a pound. (Their frozen salmon, which is not to be sneered at, in only $3.75 a pound.) Claxton's is open from six in the morning to two in the afternoon, and parking is no problem. It also has the advantage of being a few doors from Potomac Butter and Egg (220 E Street SW), where you can stock up on well-priced, reasonable quality unsalted butter (it keeps beautifully in the freezer), which is good for the hollandaise. It also carries various imported cheeses, which you must buy in specified quantities but at great savings.

Magruder's salmon is $5.99 a pound if you buy it whole. Giant's price is $5.99 a pound, whole or cut up. At Chevy Chase Seafood, salmon runs $7.49 a pound, and at Cannon's it is $7.89 a pound. Sutton Place Gourmet's price of $9.99 a pound gets the lifted eyebrow award. WILTED CUCUMBERS VINAIGRETTE (8 servings) 8 thin, medium-sized firm cucumbers 2 tablespoons salt 1 bunch dill, stripped and chopped 1/4 teaspoon dijon mustard 2 tablespoons red wine vinegar 1 tablespoon lemon juice 9 tablespoons olive oil Pepper to taste 8 boston lettuce leaves 1 jar pimento, cut into long, narrow strips (optional)

Peel the cucumbers, cut them into 3-inch chunks and scoop out the seeds (use the parer or a demitasse spoon). Slice the cucumbers as thinly as possible, turn into a bowl and sprinkle with about 2 tablespoons salt. Weight them with a dish and let them stand for 1 hour or more.

The cucumbers will shrink and a large amount of water will be in the bowl. Turn the cucumbers into a colander, rinse quickly with cold water and drain off as much water as possible. Then dry them in a dish towel, which is easier and more efficient than paper towels.Put the cucumbers into a bowl and add the dill.

In a second bowl, add the mustard and whisk in the vinegar, lemon juice, oil and pepper. Pour over the cucumbers, mix and taste. You may need to add more vinegar, or oil or salt. This dish can be completed several hours in advance and refrigerated. Just before serving, arrange the lettuce cups on individual plates and divide the cucumbers among them. Use a slotted spoon if the cucumbers seem to be floating in the vinaigrette. Garnish, if desired, with strips of pimento. POACHED WHOLE SALMON (8 servings) 4 1/2- to 5- pound whole salmon For the court bouillon: 4 quarts water 3 cups dry white wine 3 carrots, peeled and chopped 4 onions, peeled and chopped Bouquest garni consisting of 6 parsley sprigs, 2 bay leaves, 1 teaspoon thyme 1 teaspoon peppercorns 2 1/2 tablespoons salt Paper-thin lemon slices and sprigs of dill for garnish

Combine the ingreidents for the court bullion and bring slowly to a boil. Simmer for 40 minutes, remove from heat, strain and let cool.

Pour the court bullion into a fish poacher or other pot large enough to hold the fish. Wrap the salmon in cheesecloth and lower in into the liquid. Slowly bring the liquid to boil, reduce immediatley to a bare simmer, cover the pot and poach, counting 8 minutes for each pound. Turn off the heat and let the salmon sit in the liquid for about 20 minutes.

Remove from liquid, drain and place on a platter. Strain the liquid, reserving 2 tablespoons for the hollandaise (see recipe below), and freeze for future use, augumenting with 1/2 cup of water to each quart when it is to be reused. Rell the skin from the salmon, remove fins and the little sidebones. Surround with paper-thin slices of lemon and sprigs of dill. WHOLE SALMON STEAM-BAKED IN FOIL (8 servings) 4 1/2- to 5-pound salmon For the aromatic liquid: 1 cup dry white wine 1/4 teaspoon thyme 1/4 teaspoon basil 1/4 teaspoon tarragon 1/4 teaspoon rosemary 2 tablespoons chopped celery leaves 2 tablespoons chopped onion 2 slices lemon with peel Paper-thin lemon slices and sprigs of dill for garnish

Combine the aromatic liquid ingredients and simmer, uncovered, for 35 minutes.

Place a sheet of heavy-duty foil large enough to enclose the fish on a large baking pan, put the fish on the foil, bring up the sides and pour in the aromatic liquid. Crimp the foil over the fish and seal it completely. Place it in a 375-degree oven and cook for 12 minutes to the pound, or until the fish flakes.

Let the salmon sit in the sealed foil for 15 minutes. Then turn it onto a platter, peel the skin and remove the fins and the little side bones. Surround with paper-thin slices of lemon and sprigs of dill. Strain the steaming liquid and use 2 tablespoons for the hollandaise (see recipe below). Freeze the rest of the poaching liquid for future use in sauces. BLENDER OR FOOD PROCESSOR HOLLANDAISE SAUCE (4 servings) This sauce must be made in two increments to serve 8. For each recipe: 3 egg yolks 1/4 teaspoon salt 1 1/2 tablespoons lemon juice 1 tablespoon hot water or poaching stock or aromatic liquid 3/4 cup melted unsalted butter Dash of white pepper 1/2 cup heavy cream (if preparing mousseline)

Process or blend the egg yolks, salt and lemon juice with the hot water, poaching stock or steaming liquid until the eggs become thick and sticky. Cut the butter into pieces, heat it until it bubbles and let cool for a minute. Turn the processor or blender on and add the butter in a thin, steady stream. Add the pepper and blend it for 15 more seconds.

Turn into the top of a double boiler, scrape out the blender and clean it. Repeat the recipe, and add to the first batch. The sauce will keep over warm, not hot, water for about an hour. If the sauce separates, which a tablespoon or two of lukewarm water or stock into the sauce. Taste for salt and lemon.

To turn the hollandaise into a mousseline, whip 1/2 cup heavy cream until it barley mounds and fold into lukewarm hollandaise.

Note: The egg whites can be frozen in individaul ice cube cups and used for meringues, souffles or whatever. GREEN BEANS AND JERUSALEM ARTICHOKES (8 servings) 3/4 pound fresh young green beans 3/4 pound Jerusalem artichokes Lemon juice 4 tablespoons butter 1 tablespoon peanut oil Salt and pepper to taste

Cut the beans in 2 inch pieces and boil in a large pot of salted water for 6 minutes. Turn into a colander and cool quickly under cold running water. Drain and dry on a dish towel or paper towels and set them aside. (The beans can be refigerated for a day.)

Peel the Jerusalem artichokes, trim off the nobs and slice as thinly as possible. Drop the slices into a bowl of water with a littel lemon juice to keep them from turning black. Rinse, and dry them well in a dish towel before cooking.

Heat the butter and oil in a work or any pot large enough for the vegetables. When the foam had subsided, add the green beans and the artichoke slices and cook over a high flame, stirring constantly, for 2 minutes. STEAMED NEW POTATOES (8 servings) 24 small new potatoes of uniform size, unpeeled and scrubbed 2 tablespoons fresh dill, chopped 2 tablespoons fresh parsley, chopped

Use a vegetable steamer or improvise one by setting a colander in a pot. Pour boiling water into the bottom of the pot, set the steamer or colander in the pot and add the potatoes. Make sure the waer level is below the potatoes. Put a lid on the pot and steam for about 35 minutes. Test with a sharp thin knife after about 25 minutes.

Turn into a dry pot as soon as the potatoes are done and shake over heat for a minute or two.Serve in a bowl and garnish with the chopped dill and parsley. CHOCOLATE ROLL LEONTINE (8 servings) 8 ounces dark sweet chocolate 1/3 cup water Vegetable oil for the pan 8 eggs, separated 1 cup superfine sugar 1/2 cup or more good, imported cocoa 1 1/2 cups heavy cream 2 tablespoons confectioners' sugar Scrapings of 1/3 vanilla bean or a few drops of vanilla extract

Cut the chocolate into little pieces and melt it with the water over low heat, stirring until smooth. Do not let it get too hot. Set aside and let it cool a little.

Preheat the oven to 350 degrees. Brush an 11-by-17-inch jelly roll pan with vegetable oil and line it with a piece of waxed paper, leaving about 3 inches of paper hanging over each end.

Beat the egg yolks with the superfine sugar until they are light and fluffy. Mix in the melted chocolate. Beat the egg whites to soft but firm peaks. Fold the yolk-chocolate mixture into the whites, and spread evenly on top of the waxed paper. Bake for 17 minutes, or until it puffs up. Do not overcook.

Take a strip of four paper towels, fold the strip in half and wring it out in cold water. When the chocolate roll is baked, remove it immediately from the oven and place the damp towels lightly on it. Cover the wet towels with one thickness of dry paper towels and let the chocolate roll stand at room temperature until lukewarm. Remove both sets of paper towels. Slide a small knife down each side of the pan to loosen the roll. sprinkle cocoa over the top of the roll. Cover the chocolate roll with two long pieces of waxed paper. Hold them firmly with the ends of the jelly roll pan, and carefully but quickly flip the pan over so that the chocolate roll is lying on the fresh waxed paper and the lining of waxed paper is on the top. Remove the jelly roll pan and carefully and peel the lining off.

Beat the cream in a cold metal bowl. When it begins to hold shape add the confectioners' sugar and the vanilla bean scrapings or vanilla extract. Beat until the cream holds its shape.

Spoon the cream on top of the roll in three rows of three heaping tablespoons each. Then gently spread it out evenly with a spatula. Using the waxed paper, lift the long edge of the roll and roll it up like a jelly roll. Again using the waxed paper, roll it onto a long wooden board. If any cracks appear, camouflage them with more cocoa.

The chocolate roll will keep well for a several hours in the refrigerator, covered with foil a waxed paper.

PUFFED SALMON PIE (6 servings) This is a recipe for leftover salmon. 1 pound shrimp, cooked, peeled and deveined 3/4 heavy cream 3/4 cup medium-thick white sauce (see recipe below) Salt and ground white pepper, to taste 1 cup cooked salmon 2 tablespoons butter lemon juice to taste 4 egg yolks 2 egg whites 9-inch unbaked pie shell made of unsweetened pastry, refrigerated

Combine the shrimp 1/3 cup of the cream, 1/4 cup of the white sauce and salt pepper to taste. Set aside.

Puree the salmon in a food processor or blender, add the butter, the remaining cream and remaining white sauce. Process until smooth.

Turn into a saucepan and heat, stirring constantly, until a paste is formed. Season with salt, pepper and lemon juice to taste. Beat in the egg yolks. Beat the whites until they stand in soft peaks and fold into the salmon mixture.

Remove the pastry shell from the refrigerator, cover the bottom with the shrimp mixture and fill the shell with the salmon mixture. Bake at 425 degrees for 10 minutes, reduce heat to 375 degrees and bake 30 minutes more or until the pastry is brown and the filling is puffed. MEDIUM-THICK WHITE SAUCE (Makes 1 cup) 2 tablespoon butter 2 tablespoons flour 3/4 cup milk 1/4 cup heavy cream

Melt the butter in a small saucepan, stir in the flour and, stirring constantly, cook over medium heat for a minute or 2. Remove from heat and whisk in the milk. Stirring, bring to a boil. Add cream and cook another 1/2 minute.