You can use a mixer or do this with a hand whisk/by hand.

Pre- heat your oven to approx 160 degrees centigrade (fan)

Place the flour, butter, sugar and cocoa powder into a bowl.  On a slow speed combine it all, until it looks like a gritty texture.  Then add in the baking powder and combine again.  Then add the milk and egg and mix until it comes together.  Do not over mix this, but ensure that everything is combined.  I like to run a spatula around the outside edge of the bowl, to make sure there are no pockets on ingredients left.

Place the cupcake cases into a muffin tin.  Then spoon the cake mixture in, until it is around half way up in the muffin cases.

Bake for around 15-20 minutes, until the sponges have risen and they are springy to the touch.

Then let them cool properly before doing the buttercream.

To make the buttercream, mix the icing sugar, butter, cocoa powder and milk together.  On the video, I whip this up for about 5 minutes, and it makes a wonderful mousse like buttercream frosting.

Pipe on to your cupcakes and decorate as you wish!