The best cheese is your favorite cheese! Smoked gouda is a great choice for flavor and getting that perfect melty texture. Some of my other favorite options are Monterey jack cheese, mozzarella cheese, sharp cheddar cheese, pepper jack cheese, Colby jack, or just plain and simple American slices of cheese. I've even used cottage cheese before, and it melted down into a nice creamy finish. The great savory Mexican flavors of green chile pepper and egg casserole go well with almost any kind of cheese. Use what you have on hand!