The recipe for Béchamel sauce (a good sauce on its own, but also the base of many, many others) is actually quite simple, at least the original Italian one is : flour, butter and milk. You can add salt, pepper and nutmeg, as well as cheese if you feel fancy.

Edit: It's pronounced the same (and incidentally has a common etymological root), but you don't need any petals in your sauce. ;-)