IF I WERE called on to defend the virtues of freshness, one of my early witnesses would be the mushroom. The color and shape are artistically impressive. But to me its greatest virtue is a surprisingly crunchy texture and the moist, nutty flavor that emerges as you chew. It's something inveterate can-openers never will experience.

Canned mushrooms do have their place, I guess; deep in a casserole under several layers of other ingredients. But the fresh mushroom can hold center stage as well as play a supporting role. Slice it thin and arrange the medallions as an appetizer or atop a salad. Broil a handful of mushroom caps and set them atop toast triangles or on a steak. Or chop some mushrooms fine and cook them slowly with chopped onion to form the marvelously flavorful stuffing called duxelles.

Delicate creatures that they are, do mestic mushrooms must be treated with care. Don't let them linger, forgotten, in the refrigerator and wash them with care. They are easy victims to the luxurious charm of heady brown sauces or rich cream and willingly drown themselves in a spicy marinade. They are mild enough to garnish a fillet of sole, but make good foils, too, for garlic, green and red peppers and anchovies. Take the stems away and the caps become natural containers for stuffing.

If domestic mushrooms are the bunny rabbits of the vegetable counter, wild mushrooms are the hares -- racey, even gamey to taste and difficult to track. Several years ago Phyllis Richman led me to a morel hunt in the mountains of Maryland. We, walked, we stalked. Finally I trapped a single, obviously very dumb, mushroom. Phyllis found three. She had a family. At that time I did not. So I sacrificed my catch, which went, I believe, into an omelet.

Not that I feel deprived. I've eaten cepes grilled over vine cuttings in Bordeaux, meaty porcini as part of a frito mistro in Italy's Piedmont and a magical "rageout" that combined at least three different species of wild mushrooms at Alain Chapel's great restaurant near Lyons. There are those who wouldn't trade their wild mushrooms for all the truffles in Perigord. They have a point.

The recipes that follow, however, dwell mostly on domestic mushrooms. After all, what would I cook with a single wild mushroom? TO COOK MUSHROOMS

Place cleaned mushrooms (or halves or quarters) into a saucepan. Add water just to cover, plus salt, juice of half a lemon and 1 tablespoon of butter. Cover the pan. Bring water to a boil, stir, and cook 2 minutes longer. Remove from heat, uncover and let mushrooms cool in the liquid.

The juices are invaluable as a flavoring agent in sauces or a soup. Once drained, the mushrooms may be used as garniture or marinated. STUFFED MUSHROOMS (For 16 large mushrooms) 16 large mushrooms, cleaned 1 bag (10 ounces) fresh spinach 4 slices bacon, cooked, drained and crumbled 1/4 cup minced onion or 4 scallions, minced 1/4 cup minced celery 2 tablespoons bread crumbs 2 tablespoons oil (olive preferred) 1 tablespoon lemon juice, or to taste Hot pepper sauce, salt and pepper to taste Grated parmesan cheese

Wash spinach, pull off large stems and discard, then cook in salted water until softened. Drain, cool and squeeze out as much liquid as possible. Place in a bowl and mix in remaining ingredients except mushrooms and parmesan.

Preheat oven to 375 degrees. Carefully pull mushroom stems from caps and reserve stems for another use. Lightly oil the caps and inside surface of a baking pan. Bake the mushrooms for 10 minutes. (This may be done ahead.)

Stuff mushrooms with spinach filling, sprinkle parmesan over each one and return to oven for 15 to 20 minutes. MUSHROOMS IN CHAMPAGNE (2 to 3 servings) 1/2 pound fresh mushrooms, sliced 4 tablespoon butter or margarine 2 shallots or scallins, finely chopped 1/4 cup champagne or dry white wine 1 tablespoon Madeira or brandy 1/4 cup heavy cream SALT Chopped parsley

Melt butter in a saucepan. When it begins to foam, add shallots and cook until soft. Stir in mushrooms. As they begin to render juice, add champagne.

Turn up heat and let mixture come to a boil. After a minute or so, when mushrooms have become tender, remove with a slotted spoon. Keep warm.

Pour excess mushroom juice back into pan. Boil down juices and champagne to a syrup, something less than 1/4 cup. Add Madeira and cream and reduce sauce to thicken it. Taste and season as desired with salt. Return mushrooms to heat through and serve on small plates garnished with chopped parsley. ROCKFISH PROVENCAL (2 to 4 servings) 2 rockfish (about 1 1/2 pounds each), cleaned, or 2 large fillets (bluefish or snapper) 2 or 3 small tomatoes (used canned Italian in winter), chopped fine 2 cloves garlic, peeled and thinly sliced 4 shallots or scallaions, minced 1/4 cup chopped parsley 6 or 8 mushrooms caps, cooked in water Salt and freshly ground pepper to taste 1 cup mushroom cooking juice 2 cups dry white wine

Preheat oven to 375 degrees. Oil a low baking dish large enough to hold the fish. Place the fish in the pan and sprinkle over them the chopped tomato, sliced garlic, shallots and parsley. Top with mushroom caps, season with salt and pepper, then add the mushroom juice and wine to the pan. Bring liquid to a boil atop the stove, cover pan with foil and place in oven for 15 to 20 minutes, or until fish is firm. Serve with vegetables as garniture. NINA SUNDELL'S MUSHROOM RISOTTO (10 servings) 3/4 ounce dried straw mushrooms 3/4 ounce dried European mushrooms 3/4 pound fresh mushrooms, sliced 4 tablespoons chopped shallots, or 2 small onions and 2 cloves garlic, minced 6 tablespoons butter or margarine Salt, freshly ground pepper and nutmeg 6tablespoons olive oil 2cups medium-grain domestic or imported Italian rice (do not use long grain) 2 quarts homemade chicken stock or 1 quart canned chicken broth plus 1 quart water. 1/4cup dry vermouth or dry white wine 1/2 cup freshly grated parmesan cheese

Soak dried muchrooms in 2 cups wate for at least 30 minutes. Strain liquid through cheesecloth and wash off mushrooms. Saute fresh mushrooms in 2 tablespoons butter with 1 tablespoon shallots. Season with salt, pepper and a small amount of nutmeg.

Heat 3 tablespoons of butter and the oil in a large pan or casserole with a heavy bottom. Add remaining shallots and cook over meduim heat until golden. Add rice and stir until grains are well coated with oil and turn transparent. Add 1/2 cup of broth, let it come to a boil and bubble for 32 seconds. Turn heat as low as possible, stir and let cook uncovered for 10 miuntes. Add the mushrooms and their liquid. Now stir ofen, every 3 minutes or so, adding liquid as the rice begins to dry up. First add the vermouth then the remaining stock, 1 cup at a time.

At the end, the micture should be slightly soupy. Stir in the remaining 2 tablespoons butter and 1/2 cup parmesan. Serve in soup bowls and have more cheese and a pepper mill on the table.