Whether your concern is cholesterol or conservation, whether you don't eat egg yolks or ate your egg yolks yesterday, you can still have your cake -- or many an eggy treat, with just the whites. The wonderful thing about the egg is that it is divisible into its parts.

Become acquanited with the character and behavior of white. Let the whites accumulate and use them for meringues, angel and white cakes and floating islands, as well as in dishes that call for more whites than yolks.

Egg whites, if put into a covered container will keep up to a month in the refrigerator and can be frozen for indefinite periods. Eight egg whites make a cup, so 1 white is 1/8 of a cup and so on. When you have more whites than you need for current use, freeze them in a square one-cup plastic container. Once frozen you can slide the block from the container and cut into fourths or eighths and be sure of the exact measurements. They do not freeze too solidly to cut with a sharp knife. Always remember that whites give much move volume when beaten at room temperature.

When making a souffle that calls for 1 or 2 more whites than yolks, don't break eggs for the extra whites, instead reach into your refrigerator or freezer. So, too, when making an egg white dessert to be served with a custard sauce. Use the whites that remain from the custard and take the extras from your accumulated supply. ILE FLOTTANTE (floating Island) (6 Servings)

This aristocrat of French desserts is so named because the mass of baked egg whites is make to float on a custard sauce. For those who must avoid all egg yolks the island can as easily be floated on a fruit sauce. Or, if you have baked the whites in a caramel-lined mold, which is the most beautiful way, those who can't eat the custard will find the caramel drippings sufficiently satisfying as a sauce.

To caramelize the mold, put 1/4 cup granulated sugar into a heavy bottomed skillet, place over low heat and, without stirring, but swirling the pan frequently, allow the sugar to melt and then to caramelize. When the caramel is a good amber color pour it into the mold, turning the mold as you pour so caramel is evenly distributed. Allow to cool.For the recipe below use a 2-quart cylindrical mold 4 to 5 inches deep.

If you do not want the caramelcoated mold, butter the mold, roll sugar in it and knock out the excess. 8 egg whites (1 cup) 1/4 teaspoon salt 1 cup sugar Custard sauce (recipe follows)

Beat the egg whites and salt until soft peaks are formed. Then gradually, a tablespoon or 2 at a time, beat in the sugar. Beat until all the sugar is added and the mass forms stiff peaks.

Turn the mixture into the prepared mold and set it in a pan of hot water. Bake at 325 degrees for 30 to 40 minutes. The Ile is done when it shows a line of shrinkage at the sides. Cool, then refrigerate for at least 3 hours. It will shrink a bit as it cools. Run a knife around the edge and reverse onto a custard sauce. If using a fruit sauce, omit the caramel. CUSTARD SAUCE Creme Anglaise (2 cups) 1/3 cup sugar 4 egg yolks 1 1/2 cups boiling milk 2 teaspoons vanilla extract

Gradually beat the sugar into the egg yolks and continue beating until the misture is pale yellow and very thick. Continue to beat and, drop by drop at first, pour on the boiling milk. Pour the misture back into the milk pan and set over moderate heat. Stir slowly and continuously until the sauce thickens just enough to coat the spoon. Never permit the custard to boil or it will curdle. Add vanilla. Cool and then chill. MERINGUE SHELL FOR TARTS (6 servings)

When filled with a tart lemon filling the meringue shell is the traditional Angel Pie, but is a very versatile shell and is lovely and delicious with any number of fillings: diced fresh fruit, fruit compote, ice creams or flavored cream fillings.

The shell itself can be varied by the addition of 1/2 to 1 cup of ground nuts or 1/2 cup of coarsely grated semi-sweet chocolate. 4 egg whites (1/2 cup) 1/4 teaspoon cream of tartar 1/8 teaspoon salt 1 teaspoon vanilla 1 cup sugar

Beat the egg whites, cream of tartar, salt and vanilla until soft peaks are formed. Then gradually, 2 tablespoons at a time, beat in the sugar until all the sugar is added and stiff peaks are formed. Spread in a greased 10-inch pie plate. Building up the edges to form a shell. Bake for 20 minutes at 275 degrees and then 40 minutes at 300 degrees. Permit to cool in the oven with the door open. Fill as desired. Chill before serving. CHOCOLATE CHIFFON (6 Servings)

This may be molded and served as a bavarian cream or it may be mounded in a pie or tart shell, pastry or meringue. 2 envelopes gelatin 2 1/2 cups milk 2/3 cup sugar 1/4 teaspoon salt 9 ounces bittersweet (semi-sweet) chocolate 2 tablespoons cream 5 eggs whites (1/2 cup plus 2 tablespoons egg whites), stiffly beaten. Whipped cream and sweet chocolate for garnish

Soften the gelatin in 1/2 cup cold milk. Heat 2 cups milk with the sugar and salt. Add the softened gelatin to the hot milk and stir until dissolved. Cool. White it is cooling melt the chocolate with the cream over low heat, being careful not to let it scorch, then stir it into the gelatin mixture. Chill. When it is just beginning to jell, beat it until frothy and then fold in the stiffly beaten whites. Pour into a greased 7-by-3-inch deep mold just large enough to hold the mixture. Chill for at least 4 hours. Unmold on a serving dish, garnish with whipped cream and shaved or grated sweet chocolate. CHEESE PUFF (6 servings) Butter and finely grated swiss or cheddar cheese for lining mold 3 1/2 tablespoons margarine 4 tablespoons flour 1 cup hot milk 1/2 teaspoon salt 1/8 teaspoon grated nutmeg 10 egg whites (1 1/4 cups) 1 1/2 cups coarsely grated swiss or cheddar cheese

Butter an 8-cup souffle mold and sprinkle with finely grated cheese. Melt the margarine, stir in the hot milk and seasonings. Boil, stirring, for 2 minutes. Remove from the heat. Beat the egg whites until stiff peaks form. Stir 1/4 of the stiff egg whites into the cream misture along with the coarsely grated cheese. Fold in the remaining whites. Spoon the mixture into the prepared souffle dish. Bake at 375 degrees for 30 to 35 minutes, until the souffle has puffed and browned. Serve immediately. ANGEL FOOD CAKE

For variety try substituting 1/2 cup sifted cocoa for 1/2 cup of the flour called for in the recipe, and have a chocolate angel food. It is delicious coverd with whipped cream and shavings of sweet chocolate or as a base for vanilla or nut ice cream. 1 1/4 cups sifted cake flour 1/2 cup plus 1 1/3 cups sugar 1 1/2 cups (12) egg whites at room temperature 1 1/4 teaspoons cream of tartar 1/4 teaspoon salt 1 teaspoon vanilla 1/4 teaspoon almond extract

Measure sifted flour, add 1/2 cup sugar and sift 4 times. Combine egg whites, cream of tartar, salt and flavorings in a large bowl. Beat at high speed of electric mixer or rotary beater until moist soft peaks form. Add remaining 1 1/3 cups of sugar in 4 additions, beating until blended after each addition. Sift in the flour mixture in 4 additions, folding in with a large spoon; turn bowl often. Pour into ungreased 10-inch tube pan, Bake at 375 degrees for 35 to 40 minutes. Cool the cake upside down in a pan on a cake rack. Then loosen from sides and remove.