Preheat oven to 180 degrees C. Line patty tins with paper or foil cases. Put 125g of unsalted butter and 300g of caster sugar in a medium mixing bowl and beat with electric beaters until pale and creamy. Add 3 eggs and 1 teaspoon of vanilla essence, and beat until well combined. Add 350g of sifted self-raising flour, 1 teaspoon of baking powder, 1/2 cup of milk, and 3 tablespoons of walnut oil, then fold together until just combined.

Spoon into the prepared tins. Bake for 13-15 minutes. Stand on a wire rack to cool. While the cakes are cooling, make the frosting. Sift 250g of pure icing sugar into a medium mixing bowl. Add 1 eggwhite and the juice of 1 lime. Dip or spread cooled cupcakes with frosting and decorate immediately with sprinkles.

Source: Better Homes and Gardens magazine, July 2006