Who said celery should always be relegated to the Salad Department?
Cut the bread into small cubes and soften in the milk.
Melt the butter or margarine in a skillet. Add the celery and onion and cook for 3 minutes. Add the bread and milk and heat thoroughly, then beat until smooth. Remove from the heat.
Beat the egg yolks and add to the skillet, beating well. Add the seasonings. Beat the egg whites until stiff and fold into the mixture.
Pour into a well-buttered 1-quart casserole, set in a pan of hot water, and bake at 375 degrees F for 30 minutes.