Cook noodles according to package instructions, but reduce cooking time by two minutes (to cook al dente).
Melt butter in skillet on the stove top and mix in flour; cook for about one minute.
Whisk in milk, mustard, garlic, and black pepper to the butter-flour mixture. Let the mixture start to bubble, then stir in grated cheese until completely melted.
Mix cheese, drained noodles, and vegetables in a 9"x13" casserole dish. Be sure to line casserole with cooking spray or olive oil.
Let dish cool completely before freezing. Seal with plastic wrap and lid and store in freezer.
To bake: No need to thaw in fridge. Bake for one hour at 400°F with lid on top (does not need to be sealed). Remove lid and bake for another 15-20 minutes until cheese is lightly brown on top.