For brownies and bar cookies that don't crumble or stick when you remove them from the pan, try this: Butter the baking dish, then place a sheet of parchment, also buttered, inside, allowing about two inches to extend beyond two opposite sides. Bake according to the recipe's instructions, and let cool. Pull up on the parchment to lift the dessert from the pan before cutting.
No-Stick Baking Trick
Martha Stewart Living, September 2005