Cook pasta according to package directions, omitting salt and fat. Drain.
Combine milk and flour in a medium saucepan, stirring with a whisk. Cook over medium heat 2 minutes or until thick, stirring constantly with a whisk. Add cheese, salt, and pepper, stirring with a whisk until smooth. Add pasta; toss to coat. Let stand 4 minutes.
Place bread in a food processor, and pulse 10 times or until the crumbs measure 1 1/4 cups.
Heat a large nonstick skillet over medium heat. Add breadcrumbs, and cook 5 minutes or until lightly browned, stirring occasionally. Stir in melted butter; cook 2 minutes, stirring occasionally. Sprinkle breadcrumb mixture over pasta mixture.