How to Make It
Preheat the oven to 350°. Grease either a mini muffin pan with 24 cups, or a regular-size muffin pan.
Heat 2 tablespoons of the butter in a saucepan over moderate heat. Add the flour and cook, stirring until smooth, for 1 minute. Add the milk and cook over moderately low heat, stirring occasionally, until thickened, about 10 minutes. Add the cheese and stir until it’s melted and the sauce is completely smooth. Keep the sauce warm over very low heat.
In a medium pot of boiling well-salted water, cook the pasta until al dente. Add the pasta to the cheese sauce and stir to coat completely. Divide the macaroni and cheese evenly among the muffin cups.
In a small skillet over moderate heat, melt the remaining 2 tablespoons of butter. Stir in the bread crumbs and cook, stirring, until they are golden and toasted, 3 to 5 minutes. Sprinkle the toasted bread crumbs over the tops of the macaroni and cheese muffins.
Bake until golden and bubbling, about 15 minutes. Let the macaroni cool in the cups for 5 to 10 minutes before removing them and serving.