Cook macaroni according to package directions; drain. Meanwhile, in a Dutch oven, melt 3 tablespoons butter over low heat. Stir in flour until smooth; gradually whisk in milk and seasonings. Bring to a boil, stirring constantly; cook and stir 2 minutes or until thickened.
Reduce heat; stir in cheeses until melted. Stir in sour cream. Add macaroni; toss to coat. In a small skillet, heat remaining butter over medium heat. Add bread crumbs; cook and stir until golden brown. Sprinkle over top. If desired, sprinkle with parsley.
