2Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain.
3Melt 1/4 cup butter in a large saucepan over medium heat; whisk flour, brown sugar, mustard, salt, and black pepper into butter. Pour in milk and bring to a simmer; reduce heat to low and whisk until sauce is thick and bubbly, about 5 minutes. Stir macaroni, ham, and apple slices into sauce. Spread mixture into a 2-quart casserole.
4Combine soft bread crumbs with 2 tablespoons melted butter in a bowl; sprinkle crumbs over casserole.
5Bake in the preheated oven until casserole is bubbly and crumb topping is browned, about 35 minutes.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.