2 (10 oz.) pkgs. frozen spinach
1 tbsp. finely chopped onion
1 tbsp. butter
1 1/2 tbsp. flour
1 c. milk
1/4 tsp. salt
1/2 tsp. pepper
4 eggs, separated
1 1/2 c. shredded sharp cheddar cheese

Cook spinach according to package directions; drain and press dry. Set aside. Saute onion in butter in a heavy saucepan over low heat until tender. Blend in flour, stirring until smooth. Cook 1 minute, stirring constantly.

Gradually stir in milk; cook over medium heat, stirring constantly until thickened and bubbly. Stir in salt and pepper. Beat egg yolks; add to saucepan. Add to spinach; mix lightly.

Beat egg whites (at room temperature) until stiff but not dry. Fold into spinach mixture. Spoon into a well-greased 2-quart casserole. Bake at 350 degrees for 45 minutes or until golden brown.