Steal this simple pastry chef trick to make a rectangular sheet of parchment fit perfectly into a square cake pan: Make a couple of cuts in each corner before fitting it into the dish. You won't end up with wrinkled corners on your brownies, and the excess parchment paper that's left over can serve as an easy handle to help lift them out when they're done baking. For best results, grease or spray the bottom and sides of the pan before adding in the parchment—it'll help the paper stay put. Then lightly grease the parchment itself, too, just to be sure your treats don't stick.
Now that your pan is ready, you’ll need something to fill it with: check out our collection of brownie and bar recipes for ideas.