Put the amaretti biscuits in a plastic bag and crush with a rolling pin until almost powdered. Tip the biscuits into a bowl and add the sugar, butter, eggs, flour and baking powder. Beat together until smooth and creamy.
Divide the mixture evenly between paper cupcake cases arranged in a 12-hole cupcake tray and roughly level with the back of a teaspoon. Scatter with the flaked almonds.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes until risen and just firm to the touch. Transfer to a wire rack to cool. Serve dusted with sifted icing sugar.