Stir dry mustard into white sauce; add 1 3/4 cup grated cheese and stir until melted (reserve 1/4 cup cheese for topping).
Cook elbow macaroni for six minutes; drain. Add cheese sauce to macaroni; stir. Turn into a greased, 2-quart casserole dish; stir in ham cubes. Top with reserved grated cheese.
To freeze: cover casserole with aluminum foil; seal dish in jumbo freezer bag. Freeze.
To prepare: place frozen casserole (covered with aluminum foil) in preheated 375-degree oven. Bake for 25 minutes; remove aluminum foil. Bake 25 minutes more, or until hot and bubbly.