Preheat oven to 180C/160C fan-forced. Line a 12-hole, 1/3 cup-capacity muffin pan with paper cases.
Using an electric mixer, beat butter, vanilla and sugar until light and fluffy. Add eggs, 1 at a time, beating after each addition. Add flour and milk. Stir to combine.
Spoon 1/4 cup mixture into each paper case. Bake for 25 minutes or until a skewer inserted in the centre of 1 cake comes out clean. Stand cakes in pan for 2 minutes. Transfer to a wire rack to cool.
Make Pink icing: Using an electric mixer, beat butter until pale and fluffy. Gradually add icing sugar mixture and milk, beating constantly until combined. Tint pale pink using pink food colouring.
Spread cakes with icing to form a mound. Using a butter knife, mark a line through the icing, in the middle of each cake. Spoon remaining icing into a piping bag fitted with a 8mm round nozzle. Using the picture as a guide, pipe icing onto each cake to form brains.
