Blueberry cupcakes (makes 12 muffin size cakes)Ingredients125g (4 ounces) unsalted butter, softened (sweet butter)125g (4 ounces) icing sugar, (powdered sugar)4 egg whites50g (5.2 ounces) self-raising flour100g (3.5 ounces) blueberries150g (5 ounces)...