Break bread into pieces about the size of a quarter.
Break or cut cheese into bite-size pieces.
Arrange bread, cheese and shrimp in several layers
in large greased casserole dish.
Pour melted margarine over shrimp mixture.
Combine eggs, mustard, salt and milk, blending well.
Pour egg mixture over layered ingredients
in casserole dish. Let stand, covered,
in the refrigerator a minimum of 3 hours
or preferably overnight. Bake, covered,
at 350F for 1 hour. Makes 4 servings.