Cream the butter and light muscovado sugar in a bowl until they are light and fluffy. Whisk in the eggs gradually, then sift in the flour and cocoa powder, tipping in the bran left in the sieve. Add the milk and gently fold everything together.
Line a patty tin with 12 paper cases. Divide the mixture among the cases and bake in a preheated oven at 200°C (400°F), Gas Mark 6, for 15 minutes until the cakes are risen and pale golden. Cool on a wire rack.
Remove the redcurrants from the stems with a fork and put them in a food processor. Whiz until smooth. Add half the golden icing sugar and whiz again until combined. Add the remaining golden icing sugar and blend again until smooth. Spoon the redcurrant icing on top of the cakes and finish each cake with a redcurrant sprig.