In a large pot of salted water, cook the cavatappi to al dente. Drain, rinse in cold water, and set aside.

In the same pan as before, melt the butter on low heat, and mix in the flour, then cheese, then salt, pepper, and then, slowly, milk.

Make sure that you don't ever flood the mixture with milk, which causes lumps. Only add more of the milk as the mixture thickens and incorporates the previous small dose of milk.

Incorporate the pasta into the sauce, and mix thoroughly. Serve.