This can be made in advance and popped in the oven in time for dinner. This will serve 7 - 10 people. This can be made in advance and frozen, as well. Just tightly wrap dish first in plastic wrap, then in foil and freeze. Allow to thaw on counter for a few hours or overnight in fridge. Remove plastic wrap and foil before baking ... reserving foil to loosely cover dish during first part of baking.
Preheat oven to 350º.
In large pot, cook a box of elbow noodles until halfway done in heavily salted water. Drain water and pour noodles into a greased 9 x 13 casserole dish.
While the noodles are cooking, melt a stick of butter in a large sauce pan on medium heat.
Sprinkle in all-purpose flour ... roughly 2 - 3 tablespoons.
Next, add 3 - 4 cups of whole milk or a combination of milk and heavy cream to butter and flour mixture.
Whisk until cream sauce is smooth. Bring to a slow, low boil.
Reduce heat to low and season with salt, pepper and just a pinch of nutmeg (freshly ground is best!).
Begin to add about 1 pound of cubed Velveeta cheese. Whisk to incorporate and melt the cheese.
A hefty dollop of sour cream can be added at this point for a tangy addition, if desired.
Check for seasoning and adjust accordingly.
Turn off heat and pour sauce over elbow noodles in casserole pan. You'll want the sauce to completely cover the noodles. Mix a bit to blend cheese sauce well into the noodles.
Sprinkle a cup or so of shredded cheddar cheese over top of casserole.
Cover the whole dish loosely with aluminum foil and bake for about one hour at 350º or until browning is just beginning on edges and top.
Uncover and continue to bake for 10 - 15 extra minutes or until cheese is all G.B.D. (golden, brown and delicious) on top.
Remove from oven and allow to sit for 5 minutes before digging in!