JUST as the Empire State Building stands in the shadow of the World Trade Center, and Atlantic City ranks second in glitz to Las Vegas, french toast has become the dowdy and forgotten breakfast food, at least where there are croissants. Short of elevating the Empire State, it's time to revive the underdog; the easiest place to start is with pain perdu--or lost bread--as it's called in French.

The bread and the name may be French, but recipes for using up lost (stale) bread rarely appear in the cuisine's cookbooks. Instead, New Orleans' Creole cooks have elaborated and publicized the dish, frequently spiking the batter with orange blossom water and serving it alongside meat dishes.

As part of a Sunday brunch or as a dessert after dinner, it's the sweet version that creates hedonism out of a simple procedure. The following are just guidelines to be mixed and matched (the variations-on-a-stale-bread theme are numerous). Who knows? When the possibilities wear thin, there're always quail eggs and party rye. THE BATTER

The basic batter: A good egg to milk ratio is four to one: four eggs to one cup of milk. The eggier the batter, the better it will stick to the bread. A more liquid batter--one with more milk--is better for staler bread, but too much milk will make any bread mushy. Or:

* Use light or heavy cream instead of milk, but double the amount of eggs, i.e. four eggs to a 1/2 cup of cream.

* Use only egg yolks with either milk or cream for a thicker, richer batter.

* Make a milkshake batter: In a blender, combine a half pint of ice cream, 2 tablespoons milk or cream, 2 eggs, 1 tablespoon chocolate syrup and a dash of nutmeg. Dip bread (makes enough for about 6 slices) in batter and saute' in butter. Serve with ice cream or freshly whipped cream.

* Use eggnog as the batter. ADDITIONS

Per 1/2 cup batter, add:

* 1/8 to 1/4 teaspoon of any sweet spice such as cinnamon, cloves, nutmeg, ginger, anise.

* 1/2 teaspoon vanilla, or any of the fruit essences such as strawberry or pear.

* 1 1/2 teaspoons of liqueur such as brandy, Grand Marnier, framboise, Frangelico.

* 1 1/2 teaspoons lemon juice and grated rind from 1/2 lemon. Ditto for limes or oranges or other fruit juices. THE BREAD

French toast need not be made with stale bread; fresh bread will work as well, but remember that the fresher the bread, the quicker it will absorb the batter and fall apart. (That, of course, can be rectified by slicing it thick or dipping only momentarily.)

Aside from homemade bread, store-bought raisin bread and challah make excellent french toast; as does french bread. Cut the bread in different shapes: halve diagonally, cut off the crusts, cut the bread into strips. THE COOKING

Besides saute'ing in butter or oil, the batter-dipped bread--especially french, sliced thick and on the diagonal--gets puffy and crusty when deep-fried. Fill a heavy skillet about halfway with oil, and when very hot add the bread. It only takes about one minute per side to turn golden brown.

Or try baking the bread--after dipping, place in a shallow casserole dish and cook at 450 degrees for about 10 minutes. THE TOPPING

There is more to breakfast than maple syrup or confectioners' sugar. Other possibilities include:

Applesauce or apple butter

Jams like blueberry, peach or raspberry, or marmalade

Honey, especially flavored honeys

Pure'ed fruit sauces made with fresh fruit

Plain or flavored whipped cream

Fillings you would make for a pie, such as apple or peach

Make an ice cream sandwich, using a scoop of ice cream between two pieces of french toast

Toasted almonds or other nuts

After the improvisations, here are a few ready-to-go recipes. CHOCOLATE FRENCH TOAST (4 servings) Oil for deep frying 4 slices challah or other bread 2 eggs, well beaten 1/2 cup milk 1/2 cup crumbled Carr's Wheatmeal Biscuits or graham crackers 4 ounces milk chocolate Whipped cream for serving

Fill a heavy skillet about halfway with oil and heat until very hot. While oil is heating, slice challah in half diagonally. Combine eggs and milk. Just before you are ready to deep fry, dip the challah in the egg mixture and coat on both sides with the biscuit or graham cracker crumbs.

Deep fry the bread, turning once, about 1 minute on each side, or until golden brown. Remove from skillet with a slotted spoon and drain on paper towels.

Place 1 ounce of chocolate on each of the 4 bread halves and cover each half with the remaining half. Bake at 300 degrees on a greased cookie sheet for about 5 minutes, or until chocolate is melted. Garnish with whipped cream. OVERNIGHT FRENCH TOAST (3 servings) 3 large eggs, beaten 1/2 cup milk 1/8 teaspoon baking powder 1/8 teaspoon ground nutmeg 6 slices bread, cut 3/4- to 1-inch thick 2 to 3 tablespoons butter

Combine eggs, milk, baking powder and nutmeg in a bowl. Place the bread slices in a 9-by-13-inch baking dish and pour the mixture over them, turning the bread so that each slice becomes coated on both sides. Cover the dish with waxed paper and press the paper down slightly on the soaking bread to seal it. Refrigerate overnight.

When ready to cook, melt the butter in a large skillet and fry the bread slices. Cook until golden brown on both sides and serve hot with a topping of your choice. PAIN PERDU (4 servings) 5 eggs, well beaten 1/2 cup orange flower water 3 tablespoons brandy 1/2 teaspoon grated lemon rind 6 slices stale bread, crusts trimmed off, cut into strips 3/4 cup bread crumbs Oil for frying

Combine beaten eggs with orange flower water, brandy and lemon rind. Dip the bread strips into the egg mixture. Squeeze gently by pressing between two spatulas to keep them from getting too moist, dip into bread crumbs and fry in hot oil until golden, turning once.

Serve with the meat course or sprinkle with confectioners' sugar and serve as a dessert.

Adapted from "The American Regional Cookbook"