Heat oven to 180C/160C fan/gas 4.
Line a 12-bun tin with fairy cake cases.
Put the sugar, butter, flour, eggs, vanilla
and banana in a big bowl together.
Beat with an electric whisk until banana
is mashed and everything mixed. Divide
between the cases and bake for
20-22 mins until a skewer poked in
comes out clean. Cool.
To decorate, mix the icing sugar with
enough water to be spoonable, but not
too runny or it will dribble off the cakes.
Spread some over each cake. Knead
some food colouring into the regal
icing to make a bright red colour. Roll
12 different-size balls, dip one side or
the top of each in some sprinkles and
stick one on each cake.