Melt the butter over medium heat in a large saucepan. Add the flour and stir about a minute.
Add the milk and stir until it thickens a bit.
Now add the cheese and stir until blended. Its ready to eat, just mix with the noodles. If you prefer you can bake it in a 350° oven for 15 minutes in a greased casserole dish (uncovered). We prefer it fresh off the stove, its creamiest then!