1. Preheat the oven to 425°F. Cook the pasta according to package directions until al dente, drain and set aside. Meanwhile melt 4 tbsp butter in a saucepan over low heat. Whisk in the flour and cook for about 5 minutes mixing frequently to create a roux. Gradually whisk in the milk, add the bay leaf and cayenne pepper and simmer over low heat for 5 minutes, continue to stir until sauce thickens. Meanwhile, toast and crumble the bread and set aside.
2. Remove the sauce from the heat and toss with the pasta and cheese. Transfer to a greased 9-inch x 9-inch oven-proof dish and sprinkle the breadcrumbs on top. Bake for about 20 minutes, or until pasta is bubbling and golden brown.
Per serving: 685 calories, 38g fat, 24g saturated fat, 108mg cholesterol, 457mg sodium, 60g carbohydrate, 3g fiber, 6g sugar, 26g protein