1 stick of butter
1 cup of heavy cream
1 fist-sized chunk of parmesan, grated
as much garlic as you think you can stand, minced
It's important that the parmesan be of high quality, which is why I recommend the parmesan be freshly grated rather than purchased in a canister.
Melt the butter in a medium sauce pan on medium heat. Add the garlic to give it a chance to impart its flavor. Add cream and let simmer until the butter and cream have mixed fully. Slowly add the parmesan, stirring constantly. If you start melting at the same time as you start the water boiling for pasta, the sauce and pasta should be done at about the same time.
It's important that this never scald or boil over - it will develop undisolvable bits and rapidly turn into a lump of cheese in a milk bath.
Your arteries will hate me for this.