You’ve got it right, soozycue520. Food for the Gods.
In my recipe above, didn’t mention salt and dry mustard. In addition, there should also be enough black pepper to be noticeable, but not so much to overwhelm the taste of cheese. The chunks of Cheddar baked in the dish should be fairly large. You want the contrast of the browned crust and the melted cheese pockets below with some of the pasta bathed in little more than the white sauce.