Heat the oven to 190C/fan 170C/gas 5. Arrange paper cases in bun tins. Put all the cake ingredients in a large bowl and beat for about 2 mins until smooth. Divide the mixture between the cases so they are half filled and bake for 12-15 mins, until risen and golden. Cool on a wire rack.
Mix the icing sugar and water until smooth and use a third on eight of the cakes. Divide the rest in half, and colour one half pale green and the other half pale pink. Decorate the white ones with crystallised violets, the pink ones with the roses and the green ones with the wafer flowers. Leave to set. Will keep for up to 2-3 days stored in an airtight container in a cool place.