In a large pot cook pasta according to directions, drain and leave sitting in a colander.
In the empty pot melt the butter over medium high heat (about 1 minute), when butter is almost all melted add in flour, salt and pepper and then whisk until it is a paste-like consistency, then slowly pour in the milk, still whisking and let it come to a slow boil (about 4-5 minutes).
As soon as the milk starts to boil, add in the cheese and stir a few times, if it is too thick then add in another 1/4-1/2 cup of milk, then add the pasta back into the pot and coat with the cheese sauce, let cool for a few minutes, then serve and enjoy!