Can I only make these brownies in an 8x8?
No, they can be made in a larger dish. To fill a 9x13 baking dish, double the recipe and extend the baking time by about 10 minutes. You can even make a smaller portion and have it baked in one of those mini cast iron skillets. Top it off with a scoop of homemade vanilla ice cream and some chocolate syrup for a great skillet cookie.