Prepare brownie mix according to the package directions. Or, if using my homemade brownie mix, stir together mix, oil, eggs, vanilla, and water until smooth. Remove crusts from refrigerator and fill each cavity with 1 tablespoon brownie batter. If you’re using my homemade brownie mix, you’ll have exactly enough. If you’re using a box brownie mix, you’ll have some leftover. (You can make mini brownies using a muffin tin with the leftover.)