Butter a 2 quart casserole. Cut the sausages in half and brown. Arrange the bread cubes in the casserole pan. Top with the browned sausage and cover with the cheese. Beat the eggs with the milk and dry mustard--pour this over the bread cubes and refrigerate overnight. Next day--mix together the can of soup, mayonnaise and pour over top of the casserole. Bake for 1 hour at 325f.