MELT 1 Tbsp. of the butter in large saucepan on low heat. Add flour and salt; mix well. Cook and stir 1 minute. Gradually add milk, stirring until well blended. Cook until thickened, stirring constantly. Add prepared cheese product and 1-1/2 cups of the Cheddar cheese; cook until melted, stirring frequently. Add macaroni; mix lightly.
POUR into 1-1/2-quart casserole; sprinkle with remaining cheddar cheese. Melt remaining 1 Tbsp. butter; toss with bread crumbs. Sprinkle over casserole.
BAKE at 350°F for 20 minutes or until thoroughly heated.