Bring a gallon of salted water to a boil. Add the pasta. Cook til al dente, drain, and set aside.
Melt the butter in the bottom of a large sauce pan over medium high heat.
Add the flour. Stir until combined and the flour is cooked, less than a minute.
Add the milk. Bring to a boil, stirring consistently.
Remove from the heat, and add the cheese and chopped up basil. Salt to taste.
Serve over the pasta or mix it all together to combine. Add freshly grated nutmeg (optional)