Heat oven to 350°F. Cook macaroni according to package directions. Drain.
Melt butter in 3-quart saucepan until sizzling; stir in flour, salt and pepper. Add half & half; cook over medium heat, stirring constantly, 5-7 minutes or until mixture boils and thickens .
Reduce heat to low; stir in cheese. Cook 3-5 minutes or until cheese is melted. Add cooked macaroni; mix well.
Spoon into ungreased 2-quart casserole. Bake 25-30 minutes or until heated through.
Add 1 cup chopped cooked ham, 1/2 cup chopped red or
green bell pepper or 1/2 cup drained mushroom stems and pieces.