In a large stock pot with lots of water (that's been salted)* cook the pasta according to package directions to aldente'. Drain the pasta well but do not rinse.
While the pasta is draining, add the butter to the stock pot, when it melts add the cubed Velveeta Cheese & pour the cooked pasta on top.
Give it several good stirs. Add ½ cup half & half and continue stirring until the cheese melts thru. Season with salt & pepper. If the cheese sauce for the pasta is too stiff, add more milk.