Preheat oven to 350 F. Cook macaroni to according package to directions. Put the butter in a microwaveable medium bowl. Put in microwave for 20 seconds until melted. Put the flour and mix with butter and add milk and whisk until well blended. Put in microwave for seven minutes until thickens. Put the cheese in flour mixture and mix well until cheese melted. Put egg, salt and pepper and mix well. Drain macaroni and put macaroni in 9X13 baking dish and put cheese mixture in macaroni and mix well. If you like to put more cheese on top. Bake for 30 minutes.