Baked Chicken Puff

1 can condensed cream of mushroom soup
1/3 cup milk
1 cup cubed cooked chicken
2 cups cooked green beans, drained
4 eggs, separated
1/4 cup shredded American cheese

Mix soup and milk in 1 1/2 quart casserole dish. Add chicken and beans. Bake in moderate oven for 10 minutes. Meanwhile, beat egg yolks well; add cheese. Beat whites until stiff and fold in egg-cheese mixture. Pour egg mixture over the top of the hot chicken mixture and continue baking for 30 minutes.