Line a 12-section muffin tray with silver or gold foil muffin cases. Put the butter, muscovado sugar, eggs, flour, baking powder, mixed spice and milk in a bowl and beat with a hand-held electric whisk for about a minute until light and creamy. Add the mincemeat and stir in until evenly mixed. Divide the cake mixture between the foil cases.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes or until risen and just firm to the touch. Transfer to a wire rack to cool.
Put the cream, sherry and icing sugar in a bowl and whip until the mixture only just holds its shape. Pile the cream over the cakes and scatter with pink and silver balls to decorate.