Allow the brownies to cool in the pan before cutting. To cut up your brownies into perfect squares use a sharp hot knife. Simple fill a jug with hot water from the tap, submerge the knife in the water for a few minutes, wipe it dry with a clean towel and slice across the tin. Lift the brownies out of the tin using the baking paper. Alternatively to create different shapes, use a cookie cutter. Mini hearts are a great idea for valentines day.