IT USED TO BE said that a European cook could put together a prize meal from the food scraps and trimmings an American would throw away. It wasn't entirely true, of course, butthere was something in it. There still is.

We no longer automatically peel every potato that isn't either a tiny new one or a big Idaho baker. We've discovered the pleasures of potato skins baked on their own.

We now know that, rather than sending fish heads and shrimp shells directly to the compost heap, we should boil them with garlic and wine and bay leaf to produce the fish stock that will enrich the next cioppino. We cherish chicken necks and backs and wing tips for similar reasons.

The wise know that the charms of giblets do not begin and end with gravy. A few packages retrieved from the innards of roasting birds and saved in the freezer can be the makings of an elegant pa te'. Giblets also lend themselves to oriental rice dishes.

Still, not everybody has stopped peeling carrots and turnips. Most people still discard a certain number of potato parings, grapefruit rinds and broccoli stems. The same goes for cauliflower leaves, lettuce cores and pumpkin seeds. There are even people so benighted as to pass up beet tops and turnip greens.

This is not to suggest that the garbage disposal should be fed nothing but silver spoons. Or even that there are civilized uses for the last olive pit and walnut shell that pass through the culinary maestro's hands.

Those who want to carve peach stones, turn avocado seeds into house plants or stuff home-made teddy bears with peanut hulls may do so. The point here is simply that there is both money to be saved and eating pleasure to be had by reclaiming some of the food now routinely dumped.

Take lettuce and cabbage cores. Once the woody outer covering has been removed, their potentialities emerge. Thinly sliced or grated, raw, they add a pleasing element to salad. Lightly cooked in a Chinese-style chicken or seafood dish, they can contribute the crunch of water chestnuts.

Cauliflower and broccoli stems follow the same rules. Peeled and cooked along with the rest of the vegetable, they add to its deliciousness with their subtle variation of texture. So do the generally discarded leaves the shopper brings home with the broccoli and cauliflower. Fine in soup or salad for those who want to eat the flowerets alone the first time around.

Potato peel, stored in a covered bowl in the refrigerator, will keep a week or so. Coarsely chopped and fried in butter or pork fat, with or without chopped scallions, it makes a superb garnish for broccoli or string beans or spinach.

Everybody knows citrus peels are worth candying for the holiday fruitcake. Fewer recognize how good candied orange, lemon or grapefruit peel can be as an any-time-of-the-year confection on its own, or as an accent to an otherwise bland fruit salad.

Nor is this all. Slivered grapefruit, tangerine, lime, lemon and orange peel also do well in salty dishes, pickled along with onions or sequestered in the carcass of a roasting fowl. A home-made version of spumoni welcomes them. While it's not necessary to save every citrus rind, one or two in the refrigerator will come in handy surprisingly often.

And don't forget the crumbs. Stale bread, frozen, is the making of french toast, bread pudding and certain pseudo-souffle's of surprising merit. French bread, however stale, can always make a contribution in an impromptu onion soup. Actually, all stale bread and cookies should go into the freezer for later use as the crumb element in gratins and desserts.

But enough of such theorizing. Here are a few specifics.

GIBLET PATE (Makes 1 cup) Packets of necks and giblets from 4 roasting fowls 1 quart water 2 cloves garlic 1 teaspoon salt 1 bay leaf 2 tablespoons sherry 1 teaspoon allspice 1 onion 2 cloves 1 egg 1/4 cup flour 1/4 pound loose sausage meat 3 scallions, chopped 1 teaspoon parsley, chopped

Remove livers from giblet mixture and set aside. Simmer necks, hearts and gizzards, covered, in water with garlic, salt, bay leaf, sherry, allspice, onion and cloves an hour or more until gizzards are tender, adding water if necessary to keep from burning. When cool, remove meat from necks and reserve, discarding skin and bones. Trim gristle from gizzards. Slice gizzards and set aside separately. Place hearts with meat from necks. Remove bay leaf and cloves from cooking liquid. Saute' livers with sausage until sausage is lightly browned. Pure'e livers, sausage, neck meat, hearts, egg and flour with onion, garlic and 2 tablespoons cooking liquid. Stir in sliced gizzards and arrange in serving dish. Garnish with parsley and chopped scallions. Chill 2 or 3 hours before serving.

POTATO PEEL DINNER (2 to 4 servings) 1 pound bulk sausage 2 cups clean potato peelings, coarsely chopped 1 bunch scallions, chopped 4 eggs

Stir-fry sausage, potato peelings and scallions until potatoes are tender. Remove excess fat with bulb baster or spoon. Break eggs on top of mixture, cover and cook over low heat 4 minutes, or until egg white becomes opaque.

PSEUDO-SPUMONI (4 servings) 1 pint vanilla ice cream

1/2 cup almonds, chopped 1 tablespoon semi-sweet chocolate, broken in small pieces

% tablespoon slivered orange peel 1 tablespoon slivered lemon peel 1/2 cup cake or cookie crumbs, any flavor but chocolate

Allow ice cream to soften enough to work in almonds, chocolate and peels. Place in individual serving dishes, top with crumbs and refreeze.

LEMON ONION RELISH (Makes 1 cup) Slivered rind 1 lemon 2 medium onions, coarsely chopped 1/2 teaspoon dried rosemary 1/2 teaspoon salt 1 clove garlic 1/2 teaspoon ginger 1/2 teaspoon tumeric 2 tablespoons white vinegar 1 sweet red pepper, chopped 4 spring onions, chopped

Simmer lemon rind, onions, rosemary, salt, garlic, ginger and tumeric in water to cover until lemon rind is tender--about 15 minutes. Cool, add remaining ingredients and chill, adding more salt if necessary. Wonderful with a grilled chop or bit of steak.

ORANGE PEEL PILAF (4 servings) Peel 1/2 orange, slivered 1/4 cup chopped green olives 1 bunch scallions, chopped 1/2 cup walnuts 3 cups cooked barley or brown rice 1 cup chicken stock

Combine all ingredients in baking dish. Cover and bake at 350 degrees 30 minutes.