1/4 c. Bisquick
1/2 tsp. dry mustard
1 c. milk
1 c. shredded process American cheese
3 eggs, separated
1/4 tsp. cream of tartar

Heat oven to 350 degrees. In small saucepan blend Bisquick and mustard. Stir in milk gradually. Heat to boiling; boil 1 minute, stirring constantly. Stir in cheese; remove from heat. Beat egg yolks slightly. Stir cooked mixture into egg yolks. Beat egg whites and cream of tartar until stiff enough to hold soft peaks. Fold into cheese mixture.

Pour mixture into ungreased 1 1/2 quart casserole. Place in pan of hot water (1 inch deep). Bake 50 to 60 minutes or until silver knife inserted 1 inch from edge comes out clean. Serve immediately and, if desired, with a tomato or mushroom sauce. Serves 4 to 6.