Heat oven to 180C/160C fan/gas 4. Line a 12-hole muffin tin with three different coloured paper cases. Tip the flour, baking powder, unsalted butter, eggs, sugar, milk, vanilla and almonds into a large bowl and beat with an electric whisk until smooth. Put a spoonful of batter into each paper case. Crumble a biscuit into each case – use one type of biscuit for each case colour, so you remember what’s in each one. Divide the remaining batter between the cases (they should be about half full), and bake for 20-25 mins or until golden and just firm. Leave to cool on a wire rack.
Make the icing by beating the butter until soft, then beat in the icing sugar. Divide the icing into three. Add the vanilla to one batch, the cocoa and a splash of milk to another, and the ginger and cinnamon to the third. Mix them all well.
Spoon each batch of icing into a bag fitted with a star nozzle (or use one batch at a time) and pipe icing onto the cakes, matching the icing flavour with the biscuit inside. Add two of the same biscuit to the top as a decoration. Will keep for up to two days in an airtight container.