I had to title this post that way but I do apologise to those who find 'cheesiness' offensive!!
Large knob butter
Half a pint of milk
Lots of cheese (gruyere, cheddar,parmesan... whatever you have, whatever you like)
Sprig of rosemary (bash it a bit with a rolling pin or knife handle)
salt and pepper
In a heavy based pan melt the butter, then whisk in the flour, it'll be lumpy but don't worry. Pour in the milk, this is now a white sauce which can be used for anything! Add the rosemary and let the sauce thicken up, salt and pepper. Then grate in the cheese, little by little until melted. Depending on what type of hob you have you may be better off taking the pan off direct heat.
Taste and season accordingly. Its so easy I guarantee you will never buy cheese sauce again! Add fried bacon for a tasty stir through!
We always serve this with gnocchi... its real comfort food! its also amazing on steak, or poured over roast potatoes!