Tastes in food change as they do in fashion. Like the basic black dress with pearls, however, one menu item is always in style: the omelette. It came to mind when I began thinking about something light and easy for a brunch at home after a big night on the town. I don't think anything can be as festive yet simple.

The souffle omelette I suggest is different from a regular omelette. First the egg whites are beaten to soft peaks. Then the yolks are mixed with an ever-so-light sprinkling of corn starch, flour, spices and herbs, and gently folded into the whites. This method puffs the omelette to impressive proportions and makes it light and creamy. If you follow the directions carefully, you can make this beautiful dish even if you are not famous for your success with an omelette pan.

It's always best to use an omelette pan if you have one. Mine is 9 inches in diameter, enameled cast iron with a wooden handle. It was made in Holland, and I have had it for 25 years or so. If you have an omelette pan, you should use it for nothing but omelettes, eggs, pancakes or crepes. If you don't have one any solid, all-purpose frying pan will do, but it must be perfectly clean-dry inside and out, and the inside wiped with an oiled cloth.

The eggs must be at room temperature for several hours before you prepare the omelette, and the butter, too, should be at room temperature.

Make one or more of the omelette fillings and keep them warm. Have your toast and coffee ready and everything else on the table before you start the eggs. The omelette should stop cooking on the serving plate. In other words, the center should be creamy and runny when you remove it from the flame. Souffle Omelette (2 servings) First filling: 2 ounces (4 slices) cooked ham, cut into 1/4-inch squares (about 1/2 cup) 1 teaspoon finely minced shallots or white parts of scallions 1 tablespoon butter Freshly ground black pepper to taste 1 tablespoon light or heavy cream

In a small frying pan, over low heat, warm through all ingredients except cream. Remove from heat, add cream and keep warm. Second filling: 1 cup sliced fresh mushrooms 2 tablespoons butter 1 clove garlic mashed to a pulp with 1/2 teaspoon salt Freshly ground black pepper to taste 1 teaspoon finely chopped green parsley (optional) 1 tablespoon light or heavy cream

Saute mushrooms in butter with all other ingredients except cream. As soon as mushrooms turn limp, but before they start to give off their liquid, remove from heat. Add cream and keep warm. Third filling: 1 cup grated cheddar or Swiss cheese 1 teaspoon flour Salt and freshly ground pepper to taste

Combine all ingredients and keep at hand, close to stove. Omelette: 4 large eggs (at room temperature) 1 tablespoon flour 1 1/2 teaspoons cornstarch 1/4 teaspoon salt 1/4 teaspoon freshly ground black pepper 1 tablespoon finely minced green parsley (optional) Pinch of tarragon or other herb 2 tablespoons light cream or half-and-half 3 tablespoons soft butter

Separate eggs, dropping whites into a saucepan over very low heat to warm them. Sift together flour, corn starch, salt and pepper. Add parsley and herbs. Sprinkle mixture lightly over yolks, in a large bowl. Beat vigorously until smooth, adding cream in small amounts.

Beat egg whites to soft peaks. With a rubber spatula, fold about 1/3 of the whites into yolk mixture. Now gently fold this mixture into remaining whites. Increase heat under saucepan to medium.

Melt half the butter in an omelette pan or frying pan over medium heat, swirl it around, and add half the egg mixture to pan. Spread mixture evenly in pan with rubber spatula. In about 30 seconds, start to shake pan gently, moving it back and forth over heat. When edges begin to firm up and center is still loose, spoon half of filling into middle of omelette, spreading it in a neat strip. With a metal spatula, fold half the omelette over the other half. Lift pan by the handle to tilt it down, and slide folded omelette onto a serving platter or warm plate. Sprinkle, if you wish, with additional parsley or paprika, and serve at once. Be careful not to overcook. Remember that eggs will continue cooking even on the plate. The souffle omelette should be creamy, even somewhat runny, in the middle.

Repeat with remaining egg mixture, and enjoy at once.