1. Preheat the oven to 400F. Cook the macaroni according to package instructions. Drain and keep warm.

2. Meanwhile, melt 2 tablespoons of the butter in a large saucepan over medium heat. Add the flour and salt and stir until the mixture is smooth. Stir in the mustard. Gradually add the milk, stirring continually.  Cook over low heat, stirring continually, until thickened, about 5 minutes.  Stir in 1/4 cup each of the Cheddar, mozzarella and Swiss cheeses.

3. Add the macaroni to the cheese mixture and mix well. Spoon into a 9 x 7-inch baking dish and sprinkle with the remaining Cheddar, mozzarella and Swiss cheeses.

4. Melt the remaining 2 tablespoons butter in a small saucepan over medium heat. Remove from the heat and add the bread crumbs; mix well.  Sprinkle the crumbs on top of the cheese. Bake until hot and bubbly, about 15 minutes.

Tip: Easy Cleanup
For quick cleanup, generously butter the baking dish before spooning in the macaroni mixture.