Cheese sauce
From James's Wiki
Method
Melt the butter in a saucepan.
Stir in the flour and cook for 1–2 minutes.
Take the pan off the heat and gradually stir in the milk to get a smooth sauce. Return to the heat and, stirring all the time, bring to the boil.
Simmer gently for 8–10 minutes and season with salt and pepper.
Stir in cheese and allow to melt. Don't re-boil the sauce or it will become stringy.