- Preheat oven to 180°C/360°F.
- Stir together the dry ingredients in a large bowl, then add eggs, milk, oil and vanilla. Mix well to form a smooth batter.
- Place a chocolate chip cookie at the bottom of all 12 greased cupcake tin, spoon a little of the mixture over the top, to just cover the cookie. Add a square of milk chocolate on top, then spoon some more mixture over the top up to 3/4 of the way.
- Bake for 15-20 minutes then leave to cool in the tray on a wire rack. When cool enough to handle, turn the tray over and serve.