First of all, preheat the oven to 170 C (Gas 3). Put the flour, sugar, baking powder, salt, cocoa and butter in a freestanding electric mixer with a paddle attachment (or use a handheld electric whisk) and beat on slow speed until you get a sandy consistency and everything is combined.

Gradually pour in half the milk and beat until the milk is just incorporated.

Whisk the egg and remaining milk together in a separate bowl for a few seconds, then pour into the flour mixture and continue beating until just incorporated (scrape any unmixed ingredients from the side of the bowl with rubber spatula). Continue mixing for a couple of more minutes until the mixture is smooth. Do not over mix.

Spoon the mixture into the paper cases until two-thirds full and bake in the preheated oven for 20-25 minutes or until light golden and the sponge bounces back when touched.

A skewer inserted in the centre should come out clean. Leave the cupcakes to cool slightly in the tray before turning out onto a wire cooling rack to cool completely.

When the cupcakes are cold, spoon the chocolate frosting on top and decorate.

To make the chocolate frosting beat the icing sugar and butter together in a freestanding electric mixer with a paddle attachment (or use a handheld electric whisk) on medium-slow speed until the mixture comes together and is well mixed. Turn the mixer down to slow speed. This can be fairly tricky as the icing sugar will go everywhere, so I normally use clean teatowel loosely wrapped around the bowl (or on top) of my handheld whisk.

Combine the milk and chocolate in a separate bowl, then add to the butter mixture a couple of tablespoons at a time.

Once all the milk has been incorporated, turn the mixer up to high speed. Continue beating until the chocolate frosting is light and fluffy, at least 5 minutes. The longer the frosting is beaten, the fluffier and lighter it becomes.