Add heavy cream, dried mustard, cayenne pepper, black pepper and salt, whisking constantly. Bring mixture to just boiling, then reduce heat and simmer for 30 more seconds.
Spoon mac and cheese into casserole dish or dishes. If you plan on freezing one, wrap it tightly with plastic wrap, label and place in freezer.
Sprinkle noodles with bread crumbs, then drizzle with melted butter. Bake at 400ºF for approximately 20 minutes, until crumbs are golden brown.
Number of servings (yield): 12