You might try some cream cheese for the creaminess. I usually use it in my mac and cheese but you will need to add something to boost the flavor up with only mozzarella, parmesan and cream cheese. If you want to stay in white cheeses you might try a sharp swiss to give it some bite. You can always add spices as well, maybe some seasoned salt, powdered ranch dressing mix, lemon pepper, garlic, whatever you like.
I could give up chocolate but I'm no quitter!