Preheat oven to 180C. Line a 12 x 1/3 cup capacity muffin tin with cupcake patties.
Using an electric mixer on medium setting, mix all cupcake ingredients except the milk. Gradually add the milk. Mix until smooth.
Divide the mixture across the 12 cupcake patties.
Bake for 15-20 minutes or until cake skewer inserted into the centre comes out clean. Allow to cool.
Beat butter with icing sugar using an electric mixer until pale and fluffy. Beat in vanilla essence and milk until smooth, adding extra milk or icing sugar if necessary. Add a few drops of food colouring and combine.
Use a piping bag to decorate brain pattern onto cooled cupcakes.