ONE OF THE enduring monuments to the nouvelle cuisine era is bound to be fish and vegetable terrines. They already have migrated from the three-star kitchens of France to the menus of U.S. restaurants, progressive caterers and food shops. This summer more and more of them probably will be appearing at local lunch and dinner parties.

These delicate creations are, after all, elegant, light (containing none of the quantities of rich fat called for in meant pates and terrines), visually home cooks, they can be prepared ahead, are made with relative ease in this era of food processors and contain so many potential vaariations that there is little fear of duplicating something served at an earlier stop on the party circuit.

Consider the texture and color appeal of a cross-section of pate containing jewel-like pieces of shellfish surrounded by green flecks of pesto. Or the vivid greens, whites and reds of vegetable pieces viewed through the prism of the flavorable, transparent aspic that encases them. The nouvelle cuisine preference for the floating food on a thin layer of sause, instead of using the sause to cover the food, heightens the visual possibilities.

The first sight of one of these creations displayed on a plate makes you think that no mere mortal could prepare one. That's not true. Patience, a little deftness and some imagination are required, but its actually easier to make these showpieces than understand the terms used to describe them. nouvelle cuisine chefs have been almost as sloppy in their use of words as they are meticulous in arranging a plate.

We can agree that the species I'm describing is made in a mold. Pate was, at first a meat pie enclosed in a pastry crust. A similar preparation of ground or chopped meat(s) baked in an earthenware mold was a terrine. Today, these two terms are used interchangably. Aspic, according to Julia Child, is a jellied sauce. It can be, as well, the term used to describe and entire dish bound with "jellied sauce." Mousses defy even vague description. According to "Larousse Gastronomique, "In cooking and confectionary this term is used of a number of very different dishes, mostly served cold and even iced, though a few can be eaten hot."

So, call it what you will and get on with making it.

"What you really have to understand," says Judith Huxley, the culinary scholar, "is all about glue. Putting in the layers is easy. The hard part is watching the finished product crumble or fall apart because the binding has been made wrong."

Several other warnings are in order.

Temperature is very important. For a fish or meat binding that uses egg white and cream, the equipment as well as the ingredients must be cold and remain so. Aspics need time to chill and set properly. Test a small amount to be sure it sets properly and will hold up at room temperature. Also, at this time of year consider when and at what point in the meal you will serve the dish. Beware of strong sunlight or a long wait in a warm room.

Delicacy is essential. Preparing a terrine is no task for an impatient cook. Aspic takes time to set properly. To obtain the desired appearance, ingredients must be arranged with care. Don't try to cram in too much. Make a second dish instead. Molding is far easier than ummolding. Take your time, but don't leave a mold in hot water too long. Be patient or you may find yourself with half a loaf. Use oiled aluminum foil as a support for especially delicate creations. If serving directly from the mold, use a flexible spatula to support each piece.

There is a danger of underseasoning. Cold temperatures diminish the strength of herbs and spices. Texture means a great deal, too, so be sure vegetables remain crisp and shellfish doesn't become rubbery from over-cooking. vSpinach or any other puree that is still "wet" is as dangerous as badly made cement.

To the accomplished cook, nuances of taste and texture become even more important. These dishes tend to honor the comtemporary dictate of simplicity. The Troigros Brothers famous terrine of legumes, for example, contains only four vegetables and is bound by a mousse of ham and egg white. But simplicity bears a cross -- flaws are readily apparent.

So aspics must be, in Escoffier's view, "at once succluent, transparent and just sufficiently glutinous to permit it being turned out of a mold without breaking." Sauces must be light and liquid. Decoration must be subdued and arranged to give an impression of spontaneity.Threads of vegetables and (in a dream) truffles have replaced the mock floral arrangements that appeared behind plate glass windows of aspic in classic presentations.

But no great dish is created in the classroom. The summer stretches ahead. The fish are jumping and the vegetables (as well as the cotton) are high. Get thee to the kitchen and take these recipes along with you.

This beautiful pate is made of fresh vegetables -- which can be varied according to the season -- lightly blanced and seasoned with a bit of salt, pepper and oil. The vegetables are combined and cooked with a mousse of chicken. The pate should be served cold, in slices, surrounded by a tomato sauce. JEAN BLANCHET'S VEGETABLE PATE WITH CHICKEN MOUSSE Mousse 3/4 pound boneless chicken breast (about 1 1/2 cups, when cubed) 2 1/4 to 2 3/4 cups heavy cream 1/2 teaspoon summer savory 1 teaspoon tarragon 2 tablespoons parsley, chopped Safflower oil 1 teaspoon salt 1/2 teaspoon pepper

Texture is very important in this dish. The secret of getting it right is to trim the chicken carefully, and to start with very cold ingredients and equipment. Before cutting the chicken into cubes, remove all traces of fat and pull and scrape out the white tendons that run down the underside of each breast. Cube the chicken and place it in the bowl of a food processor fitted with the metal blade, and refrigerate for about 1/2 hour. You can prepare the vegetables while the chicken is chilling.

Removing the bowl from the refrigertor and place it on the base of the processor. Add the summer savory, tarragon and parsley. Puree the mixture until it is smooth. With the machine running, add cold cream in a slow, constant stream. Check the texture after adding 2 cups, and add remaining cream very slowly, only until achieving a texture like whipped cream. The mixture should not be runny. Add the salt, pepper and melted glaze, if any, at the end. Set the mousse aside. VEGETABLES

You can use any vegetables that are in season. Have an eye for colors, which should contrast. The vegestables hould be prepared and lightly blanched in boiling water, then removed with a slotted spoon to drain and dry on paper towels. When cool, they should be tossed gently with salt, pepper and a little oil and placed on a large plate or cookie sheet.

We used the following vegetables in our pate: 2 small zucchini (6 ounces), ends trimmed and cut into spears, 2 medium carrots (5 ounces), ends trimmed, peeled and cut into spears, Cauliflower (6 ounces), thinly sliced, 15 green beans (6 ounces), ends trimmed, 1 large tomato (10 ounces) peeled, seeded and cut into strips.

Blanch the zucchini for 2 minutes, the carrots and cauliflower for 3 minutes and the green beans for 1 minute. The tomato need not be blanched. ASSEMBLY

Oil a 6-cup pyrex loaf mold. Cover the bottom with a layer of mousse, about 1 inch deep. Arrange a layer of vegetables on top, alternating them with respect to color and texture. Push the vegetables gently into the mousse. Cover with more mousse, then another layer of vegetables. Cover again with more mousse and vegetables, finishing the top with a layer of mousse. Cover with oiled parchment paper.

Place the mold in a slightly larger pan. Add enough water to the larger pan until it comes 1/3 of the way up the mold holding the mousse. Bake in a 325-degree oven for 50 to 60 minutes. Let cool and refrigerate at least over-night before serving. Serve in slices, surrounded by cold tomato sauce. Sauce (Makes 4-cups) 1 tablespoon chopped shallots 4 tablespoons wine vinegar 1 teaspoon tarragon 1tablespoon tomato paste 1/3 cup water 2/3 cup fresh tomato, peeled, seeded and diced (about 1 large tomato) 1 cup oil (1/2 safflower and 1/2 oilve, or to taste) 2 cups tomato juice 1 teaspoon salt 1/2 teaspoon pepper

Place the first five ingredients in a saucepan and reduce over high heat to about 1/3 cup. Cool slightly and place in a food processor equipped with the metal blade. Add the diced tomato and puree until smooth. Add the oil and process 20 seconds. Add tomato juice and process 20 seconds more. Season with salt and pepper, if needed. -- From "The Pleasures of Cooking" magazine

This shrimp mixture is a magix one: white when it goes in the mold and glowing, delicate, peach when it emerges. On a day when you don't want to bother with the vegetables, try this in individual molds to float on a watercress mayonnaise. The vegetable preparation should be done a day ahead. BARBARA KAFKA'S SHRIMP AND VEGETABLE TERRINE (18 servings) Vegetable Preparation: 3 bunches watercress, leaves only, well washed 1 zucchini, cut into julienne strips 1 cup frozen baby green peas, thawed and drained 3 or 4 artichokes

Plunge the watercress leaves into a large pot of boiling salted water. Cook for 8 minutes after the water returns to a boil. Drain in a collander and rinse with cold water. Wrap in a tea towel to drain.

Blanch the zucchini in another pot of boiling salted water for 30 seconds. Drain; refresh in cold water. Wrap in a tea towel, pressing gently to eliminate excess water.Drain the peas and wrap in a towel to eliminate excess water.

Prepare the artichoke bottoms as follows: Place the artichoke on your work surface; cut off the stem. Pull off the outer leaves and cut off the inner, rubbing the cut surfaces with lemon juice. With a small knife, cut out the choke and then trim away any remaining hard parts. Boil the prepared bottoms in acidulated water until tender when pierced with a knife. Refrigerate vegetables in towels overnight. Shrimp Mousse 1 1/2 pounds shelled, deveined shrimp 3 egg whites 1 tablespoon kosher salt 1/8 teaspoon grated nutmeg 2 1/4 cups heavy cream

Place shrimp and egg whites in a food processor fitted with the metal blade.

Process until smooth. Add salt and nutmeg. Process to mix. Place mixture in a mixing bowl, cover and chill 1 hour.

In a mixing bowl, whip the cream until soft peaks form. Using an electric hand mixer, gradually beat the cream into the shrimp mixture, adding about 2 tablespoons at a time. ASSEMBLY

Preheat oven to 350 degrees. Lightly butter a 6-cup, 9-by-5 inch loaf pan.

Spoon about 1 cup of shrimp mousse into the bottom and spread evenly. Tap the mold to settle the mousse. Lay the zucchini strips lengthwise to cover the mousse. Gently pat them down with your hands. Carefully spoon about 3/4 cup shrimp mousse over succhini and spread smooth. Lay drained watercress over the mousse to make an even layer. Cover with another 3/4 cup shrimp mousse.

Sprinkle peas and repeat with a mousse layer. Let the artichoke bottoms, curved sides up, on top. Spread remaining mousse over and around artichokes. (You may have up to 1/2 cup of mousse mixture left over. If so, bake it in a ramekin.) Cover tightly with lightly buttered foil, buttered side down.

Place loaf pan in a larger roasting pan. Fill roasting pan with very hot water going halfway up the sides of the loaf pan. Bake 30 to 35 minutes. Remove terrine from oven and roasting pan. Cool on a wire rack. Refrigerate until thoroughly cold.

To serve, unmold terrine and slice into 1/2-inch slices, using a seesaw motion with the knife. Place about 3 tablespoons Lemon-Chive Sabayon sauce (recipe follows) on each plate and top with a slice of terrine. Garnish with fresh chives. Lemon-Chive Sabayon Sauce (Makes 2 cups) 8 egg yolks 3 tablespoons lemon juice 1 teaspoon kosher salt 1/2 cup water 2 tablespoons chopped fresh chives

Place the egg yolks in the top of a double boiler and whisk for 30 seconds. Place the pot over simmering water. Whisk the yolks constantly until they have thickened and doubled in volume. Whisk in the lemon juice, salt and 1/4 cup water. Cook another 30 seconds. Stir in the chives and enough water to make 2 cups.

You can substitute watercress for sorrel, though you lose sorrel's unique acidity. -- From "The Pleasures of Cooking" magazine JANET AND ROGER YASEEN'S TERRINE OF GARDEN VEGETABLES (8 to 10 servings) 1/2 pound green beans, trimmed 4 large carrots, trimmed 6 artichokes 1 head romaine 1/2 package (10 ounce size) frozen peas Degreased chicken broth 4 envelopes (4 tablespoons) unflavored gelatin Salt and freshly ground pepper 2 tablespoons prepared white horseradish Yogurt-horseradish sauce (recipe below)

Chill a 6-cup mold in freezer. Cook green beans 7 minutes in covered saucepan in unsalted boiling water to barely cover. Drain well, reserving cooking liquid. Transfer beans to small bowl, cover and refrigerate. Boil reserved cooking liquid over high heat until reduced to 2 tablespoons.

Cook carrots in covered saucepan in unsalted water to barely cover until very tender. Drain well, reserving cooking liquid. Let carrots cool slightly, then chop coarsely.Transfer to separate bowl, cover and refrigerate. Boil cooking liquid over high heat until reduced to 2 tablespoons. Add to bean liquid. Cook artichokes in boiling salted water until tender. Drain well. When cool enough to handle, removes leaves and chokes; use hearts only in terrine. Transfer to separate bowl and chill.

Wash romaine, discarding coarser ribs. Blanch dark green leaves 2 minutes. Drain well. When cool enough to handle, shred as for cole slaw. Refrigerate. Combine bean and carrot cooking liquid with enough chicken broth to measure 3 cups. Add gelatin and let stand 5 minutes to soften. Transfer to small saucepan and heat gently, stirring until gelatin is dissolved. Remove from heat, taste and season with salt, pepper and horseradish, blending well. Remove mold from freezer and quickly swirl several tablespoons of gelatin mixture around sides and bottom (it should set immediately).

Crisscross a few green beans on bottom of mold to make a lattice pattern. Stand a few more beans upright around edge (longer ones will be trimmed later).

Layor carrots evenly over latticed beans. Top with peas. Arrange remaining beans over peas. Top with shredded romaine. Place one artichoke heart in center of mold and surround with remaining five. Slowly add remaining gelatin to mold. Refrigerate until set.

When set, trim any beans extending over mold. To serve, dip terrine briefly into pan of hot water and invert only platter. Cut into wedges and serve with Yogurt-horseradish sauce. Yogurt-Horseradish Sauce (Makes about 1 1/2 cups) 1 cup plain yogurt 1/2 cup mayonnaise 2 tablespoons prepared white horseradish or to taste

Blend all ingredients. Cover and chill.