1. Preheat the oven to 170C and line a 12 hole cupcake tray with cupcake liners.
2. In the bowl of an electric mixer add the butter and sugar and mix on a medium speed for 5 minutes until the butter is light and creamy. Sift the flour, cocoa and baking powder together and set aside. Turn the mixer down to a low speed and crack the eggs in one at a time. Once the eggs are fully incorporated add half of the flour and mix to combine, add the milk and vanilla extract followed by the remaining flour and mix again.
3. Using an ice cream scoop or two spoons, fill the cupcake liners to 2/3 full and bake for 20 minutes or golden brown and springy to the touch.
4. Allow the cupcakes to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.
5. While the cake are cooling scoop out half a tub of store bought frosting into a large bowl with the custard powder and milk and mix to combine. Set aside.
6. Once cool cut a hollow from the center of each cake using a sharp knife or an apple corer. Fill the hollow with custard cream and set aside while you make the frosting.

For the frosting:

1. To make the frosting first mix the butter in the bowl of an electric mixer until pale and soft. Add the icing sugar, custard powder, vanilla and 2tbsp of the milk. Turn the mixer on low and gradually increase the speed. Whip for 5 minutes, if the frosting looks too stiff add a splash more milk until you reach a nice piping consistency.
2. Once the cupcakes have cooled fill a piping bag, fitted with an open star nozzle, with the custard frosting and pipe a cute swirl on each cake then top with a custard cream.
3. Drizzle with melted chocolate and enjoy!