I make a bechemel sauce that can be found in the recipe you used (dry mustard, etc.), remove it from the burner and add the cheese. We have tested MANY different cheeses and we still like cheddar (sharp), monteray jack, and a bit of Parmesan. I don't bake mine. When the cheese is melted I simply add the noodles, stir, and put it in a bowl. However, we have been known to sit down with the pot in the middle and dig away!
I like it creamy and not baked in.