Spinach Souffle'

1/4 cup butter or margarine

1 cup cooked chopped spinach

1 tablespoon grated onion

1 teaspoon salt

5 tablespoons flour

1/8 teaspoon pepper

1 cup milk

3 eggs, separated

1 cup grated cheddar cheese

Preheat oven to 350. Grease 1 1/2 quart casserole dish. Melt butter in saucepan and saute' onion for 5 minutes. Blend flour and gradually stir in milk. Cook over medium heat, stirring constantly, until thick and smooth. Remove from heat. Stir in cheese, spinach, salt and pepper. In mixing bowl, beat egg yolks until thick and lemon colored. In another bowl, beat egg whites until stiff, but not dry. Carefully fold into cheese mixture along with yolks. Turn into greased dish and bake in preheated oven for 45 minutes.