Butter a 9 x 13 pan. Butter both sides of bread and lay in pan. Cover w/ 8 oz. grated cheddar cheese and 1/2 lb. diced ham. Cover w/ 6-8 more slices of bread, buttered on top only. Mix 4 eggs, milk and dry mustard and pour over the top. Let stand in fridge overnight. Bake at 325 for one hour.