"Smooth as custard" describes the ultimate in smoothness, and rightly, for properly prepared custard is just that.

Custards and puddings depend primarily on milk, eggs and cream, items that, when handled correctly, make delightful eating.

There are a few simple rules to remember when working with milk or with cream and eggs. First, for any given dessert, do not tamper with the proportion of milk, cream and eggs either in an attempt to economize or to be more lavish. Too many eggs in proportion to the liquid is likely to give you a curdled mass; too few eggs will give a runny custard. True custards are thickened by eggs alone.

Puddings have an additional thickening agent, flour or cornstarch, and are not so touchy to prepare, but care must be taken when adding the eggs to the hot mixture. Always add a bit of the hot mixture to the eggs to warm them before stirring into a pan of hot mixture.

Remember that eggs coagulate at a very low temperature. Cooking at too high a heat or for too long a time is the most common cause of failure in making a custard. When making a boiled custard, stir over low heat until mixture just coats the spoon. Do not permit it to boil or it will curdle past the point of being edible. Since most foods have to boil and bubble to cook, this is a characteristic of eggs that it is well not to forget.

It is also true when thickening a sauce with egg yolks -- never boil the sauce after stirring in the yolks. In the case of a baked custard, the bowl or cups of custard must be placed in a pan of water and baked at a low temperature. If there is danger that the water in the pan will boil, add a bit of ice or ice water to keep the temperature down. A baked custard that is porous or that separates into curd and liquid has been baked at too high a heat or for too long.

The manner in which the eggs and milk or cream have been mixed and beaten affects the consistency of the custard. If the eggs are well beaten instead of just lightly beaten, you will have a less firm custard, one that cannot be unmolded. A foam forms on top with beating, and this bakes into a beautiful brown topping. This is desirable for custard pies and for custard to be served in the baking cups. For a custard that you wish to unmold, such as a vanilla custard to serve with fruit, or a caramel custard, the eggs must be only lightly mixed, for you do not want to incorporate air into them, since the less air beaten into the eggs, the firmer and smoother the custard. CREME CARAMEL

A French classic, well deserving of its popularity, creme caramel is a custard so smooth and firm that it can be cut like a cake. It's quite tempting in appearance with its brown caramel topping and sauce.

First, coat a 1-quart souffle dish or glass casserole with caramel syrup: 1 cup sugar 1/3 cup water 1/4 teaspoon cream of tartar

Combine these ingredients in a heavy skillet or saucepan, and cook over low heat without stirring until the syrup turns amber, or a good lively brown. Now with the baking dish in one hand and the pan of syrup in the other, pour the syrup into the dish while you rotate it so that the sides and bottom are completely coated with the caramel. Set aside for the caramel to harden before pouring in the custard: 4 whole eggs 6 egg yolks 8 tablespoons sugar 1/4 teaspoon salt 3 cups hot milk 1 inch of vanilla bean or 1 teaspoon of vanilla

Break the eggs into a bowl, add the sugar and salt and toss lightly with a fork until just barely mixed. Slowly stir in the hot milk and vanilla. If using a vanilla bean, put it into the milk while heating it, discard before adding to the eggs. Pour into the souffle dish with the hardened caramel lining, place in a pan of water, and bake at 275 degrees for 2 hours or until firm. When custard is done, a small pointed knife will come out clean; or press gently with a finger tip, and if no liquid breaks through it is done. Cool and then chill in the refrigerator. Unmold on a platter to serve. To unmold, run a sharp knife all around the edge. Place the serving dish on top and, holding tightly, tip the whole upside down. Lift off the baking dish, and you will have a gold and brown mold. BAKED VANILLA CUSTARD

Make a custard as directed in the preceding recipe and pour it into a buttered souffle dish or glass caserole instead of a cramelizd one. Bake, chill, and unmold as directed. Garnish with sliced fruit or berries. BAKED CHOCOLATE CUSTARD

Follow directions for the custard in creme caramel. When heating the milk, add 6 ounces semisweet chocolate and stir until dissolved. Pour into a buttered baking dish and bake, chill and unmold as directed. CREME BRULEE

This is the richest of all the custards, a very smooth cream topped with crispy caramelized sugar. The custard must be thick and firm enough to spoon out but not of a "set" consistency. 3 cups thick cream 1 inch of vanilla bean or 1 teaspoon vanilla extract 6 egg yolks 1 1/2 cups sugar

Heat the cream with the vanilla bean in a heavy pan to just past lukewarm. If using vanilla extract, add it to the mixture at the end. Beat the eggs with 1/2 cup of the sugar until very creamy and light. Mix in the warm cream very slowly and carefully. Return to the pan, stir over a low heat until the mixture coats the back of a spoon. Pour into a shallow 2-inch glass dish. Place in the refrigerator to set for at least 8 hours, or overnight. When ready to serve, cover top completely with the remaining cup of sugar so that none of the cream shows through. Place the dish on a bed of crushed ice and place under a broiler until all the sugar is caramelized. STANDARD CREAM PUDDING OR FILLING

This is an excellent cream for use in all cream pies, such as coconut cream, banana cream or cream with a fruit or berry topping. It is also ideal for such desserts as trifles or filled cake. 3 eggs yolks 1/3 cup sugar 1/8 teaspoon salt 2 1/2 tablespoons cornstarch 1 tablespoon butter 2 cups scalded milk 1 teaspoon vanilla

Beat the yolks until light, then beat in the sugar, salt, cornstarch and butter. Add a bit of the hot milk to these ingredients and then carefully stir them back into the pan of milk. Cook over low heat, stirring constantly until it thickens, that is, until a spoon pulled through will leave a slight path. Add the vanilla. Cool and it is ready.

When making a coconut or banana cream pie, add the coconut or bananas as soon as you remove from the fire. CREME ANGLAISE, or CUSTARD FOR SAUCES

Why this should sometimes be referred to as a boiled custard is a bit of a mystery, for at no time must it be allowed to boil. 4 egg yolks 1/4 cup sugar 1/8 teaspoon salt 2 cups scalded milk 1 teaspoon vanilla or other desired flavoring

Beat the egg yolks slightly, add the sugar and salt. Stir a little of the hot milk into the yolks to warm them and then carefully stir the egg mixture into the pan of milk. Cook, stirring constantly over very low heat until the custard coats the back of a spoon. Never or any account allow it to boil or it will curdle badly.

In fact, if allowed to stay on the heat for even a second after it coats the spoon, it will curdle a little and not be as good or as attractive to serve. Add flavoring. Strain and cool the custard before using. It will thicken appreciably as it cools.