Step 1

Preheat the oven to 180°C. Lightly grease a 12-hole square muffin or friand pan.

Step 2

Sift the flour, cocoa powder and bicarbonate of soda together, then stir in the sugar.

Step 3

Place the butter and cola in a saucepan over low heat, stirring until the butter has melted, then add to the dry ingredients with the milk, eggs and vanilla extract. Divide mixture between the pan moulds and bake for 18 minutes or until a skewer inserted into one of the centres comes out clean. Allow to cool completely on a wire rack.

Step 4

When ready to serve, carefully slice the top off each cake and set aside.

Step 5

Scoop out a little of the filling, then fill each hole with some chocolate coins and replace the lids.