Preheat oven to 350.
Cook macaroni as directed on package& drain.
While macaroni is cooking, melt butter in 4 quart saucepan, over low heat. Stir in flour, salt and pepper. Cook over medium heat, stirring constantly until smooth and bubbly.
Remove from heat and stir in milk. Heat to boiling over medium heat, stirring constantly. It will take a long time!
Stir in cheese until melted.
Pour cheese sauce over drained macaroni, mix, and pour in to 4 quart casserole or 9x13 pan.
Sprinkle with cracker crumbs if desired.
Bake uncovered for 20-25 minutes.