This is my recipe:

Grease a 8X8 pan with butter. Put in a layer of cooked macaroni (al dente). Sprinkle the layer with some flour, salt and pepper, grated sharp cheddar cheese, and dot with butter. Put another layer of macaroni, and layer the same. The top layer will just be macaroni with cheese, butter, and salt and pepper (no flour). Then fill the pan about 3/4 full with milk. I use 2%, but whole milk will make it creamier. Sprinkle top with bread crumbs and dot with butter. Bake at 350 degrees 45 minutes to an hour, till it is the consistency you like. (the milk kind of bubbles up through the casserole and makes its own sauce).