In a small bowl, beat egg whites and salt until stiff peaks form. In a large bowl, beat the cornstarch, egg yolks and pepper until lemon-colored. Add water; mix well. Fold in the egg whites.
Pour into two greased 9-in. pie plates. Bake at 350° for 15 minutes or until a knife inserted in the center comes out clean.
Meanwhile, in a small saucepan, melt butter. Stir in the cornstarch, salt and pepper until smooth. Gradually add milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Reduce heat; stir in cheese until melted.
To serve, cut each omelet into six wedges. Stack two wedges on each serving plate with cheese sauce drizzled between and on top.