Beat egg whites until frothy.

Add water and salt and beat until stiff, but not dry.

Beat egg yolks until lemon-colored and very thick.

Gently fold yolks into the whites.

Heat butter in a 10" skillet with oven proof handle.

Pour in the egg mixture, spreading it evenly, but slightly higher around the edges.

Reduce heat and cook slowly about 8 to 10 minutes, or until omelet is puffed up and set.

Gently lift up on edge of it with a spatula; it should be golden on the underside.

Bake in a 325° oven for about 10 minutes, or until a knife inserted in omelet center comes out clean.

Loosen omelet around edges with spatula. Tilt pan and fold the smaller, or upper half, over the lower half.

With the aid of spatula and spoon, slip omelet onto hot platter.

Spoon Cheese Sauce on it and serve at once.

To make cheese sauce:.

Melt 2 tablespoons butter in saucepan over low heat.

Blend in 2 tablespoons flour, 1/4 teaspoon salt and a dash of black pepper.

Add 1 cup milk all at one time and cook and stir until mixture bubbles and thickens. Add 1 cup shredded sharp cheese and stir until it melts.