How to powder cheese?

[Vitriola]

I really don't want to powder some cheese, but I do want my potatoes au gratin to not look so...undone. Thye taste great, they were cooked through, but the cheese does not seem to want to make that creamy kind of sauce that box potatoes do. Is this just a telltale sign that it is homemade? Did that 1t flour I put in and mixed in thoroughly responsible for this? Everything about the recipe (potatoes, milk, cream, flour, butter, salt) is great, I just want it to look more appetizing.