1. Line a large baking tray with baking paper or plastic wrap.
2. Place the cake or pudding in a food processor and pulse until it is the consistency of rough crumbs. Or, crumble the cake with your fingers and then mash with a fork
3. Roll the mixture into 20 small balls.
4. Place the dark chocolate in a small, shallow microwave-safe jug and microwave on low for 1 minute. Stir and repeat until the chocolate is melted.
5. Use a fork to dip and cover each pudding ball in chocolate, then place on the baking tray.
6. When all of the balls are covered in chocolate, place the tray in the fridge to set.
7. Place the white chocolate in a small, shallow microwave-safe jug and microwave on low for 1 minute. Stir and repeat until the chocolate is melted.
8. Spoon the melted white chocolate over each truffle and gently press a piece of cherry on the top of each one.
9. Return the truffles to the fridge to set.