Brush a 20 cm (8 inch) square or round cake tin (not one with a loose base) with melted butter. Fold a piece of greaseproof paper in half lengthways and wrap around the tin, folded-edge-downwards. Cut the paper so it is 4 cm (1½ inches) taller than the tin and the end is 2 cm (¾ inch) longer than the circumference. Snip cuts along the folded edge of the paper and place,