Ach! I forgot you don't have electric kettles in the US because of some crappy power supply issues! When making any kind of pasta, I boil the water in a kettle first, then pour it into a pan on the hob (aka stove) - so pasta starts cooking in 3m or so.

Anyway, without a kettle I guess it's still doable around the 20m mark, as long as you have a gas or induction hob, and while the pasta is cooking you grate the cheese and make the sauce.

And on the sauce, I make a roux, add full-fat milk, add the cheese and season - easy. If you want to get fancy, chopped onions and chunks of pre-cooked (or tinned) ham mixes things up.