I make mac & cheese with Velveeta. Yes, I know it is a travesty. But Velveeta melts and kids will eat it.
I make a roux with butter, flour, and onions, and add milk. Then turn off the heat and add the cubed Velveeta.
I also need to keep some extra cubes on the counter out of the reach of little fingers that sneak in and steal the cheese cubes off the cutting board.