in a large pot boil your macoroni noddle for 7 to 10 mins add a little salt to the water to flavor your pasta
in a large sauce pan melt your butter on med high heat once your butter is melted add your flour and mix them together with a wooden spoon once your flour and butter have formed a slight paste you want to add your 3 cups of milk your pepper and your ground mustard bring to a slight boil then reduce your to a med to low heat and add your 2 cups of mild cheddar and white sharp cheddar keep an eye on your cheese sauce stiring it until it slightly thick . while your sauce is cooking drain your noodles and put them back into the same pot you cooked them in once your cheese sauce is done pour your sauce onto your noodle and mix together well
preheat your oven to 350 degrees and spray your casserole dish with pam . pour your mac and cheese into your casserole dish and sprinkle the top with your cobly cheese bake for 15 to 25 mins or until bubbley and the cheese on top has melted ... enjoy
if you have a 32 oz or bigger box of noodles i would use half the box .