A 9x9" brownie recipe will crumble and press into the perfect crust for a 9x13" cake. If you only make 9x13 brownies that's fine - just crumble and use only part of it. My ice cream recipe is about 1 1/2 quarts, but you can use whatever you like that fits in your pan. Just keep in mind the thicker it is the more difficult it is to slice.