A staple at English boarding schools, these individual cakes are served with afternoon tea. They don't keep well; after a day they take on the characteristics of "rocks". Preheat oven to 200ºC (205C). Grease a large baking sheet; set aside. Sift flour, baking powder, salt, nutmeg, cinnamon and cloves into a large bowl. With your fingers, rub in butter and shortening until mixture is crumbly. Stir in raisins, walnuts, brown sugar, and lemon peel. Add egg and just enough milk to make a stiff dough. Drop tablespoonfuls of dough 5 cm apart on baking sheet. Bake dozen to 15 minutes or until golden brown. Transfer to a wire rack to cool. Serve fresh. Makes about 15 rock cakes.