Melt butter in saucepan and stir in flour until smooth. Gradually whisk in the milk, heat until boiling and immediately turn down the heat. Simmer for a few minutes and add pepper and hot sauce, and stir in the evaporated milk. Continue simmering a few minutes and then melt about 3/4 of the cheese into the sauce. Combine sauce with cooked macaroni in a 9 x 13 inch baking dish. Sprinkle the remaining cheese over the top and bake at 350 degrees for 30 minutes.