Cook macaroni as directed on package, omitting salt and reducing the cooking time by 2 min. Rinse macaroni under cold water; drain. Combine shredded cheeses; reserve 1/2 cup for topping.
Melt 5 Tbsp. butter in Dutch oven on low heat. Add flour; mix well. Cook 2 min. or until hot and bubbly, stirring constantly. (Do not cook until browned.)
Whisk milk gradually into butter mixture; cook on medium heat 5 min. or until sauce comes to boil and thickens, stirring constantly. Remove from heat.
Add remaining shredded cheese mixture to the sauce along with the VELVEETA, blue cheese, mustard and 2 Tbsp. Parmesan; cook 3 to 5 min. or until VELVEETA is completely melted, stirring constantly. Add macaroni; mix well. Spoon into 13x9-inch baking dish sprayed with cooking spray.
Melt remaining butter; mix with bread crumbs, reserved shredded cheese mixture and remaining Parmesan. Sprinkle over macaroni mixture.
Bake 25 to 30 min. or until top is golden brown, and macaroni and cheese is hot and bubbly around edges.