Preheat the oven to 200C/190C Fan/Gas 6. Fill two 12-hole cupcake tins with paper cases.
In a large bowl, beat the butter, sugar, flour, baking powder and salt using an electric whisk until the ingredients are well incorporated.
Whisk the milk, vanilla essence and eggs in a jug. Pour three-quarters into the dry ingredients and beat slowly using an electric whisk until combined. Increase the speed, pour in the remaining milk mixture and beat until you have a smooth batter. Stir in the bananas.
Divide the batter evenly between the 24 cupcake cases and put a brazil nut into the centre of each one. Bake for about 20 minutes, or until the sponge bounces back when lightly pressed.
Leave to cool slightly in the tin before transferring to a wire rack.
For the decoration, roll out the flesh-coloured icing and cut into circles to fit the top of the cupcakes. Roll out the black fondant icing and cut to resemble the geishas’ hair. Top each cupcake with a circle and use the edible ink pen to draw on facial features. Attach the hair using edible glue or a little water.