Melt the butter a microwave safe bowl large enough to cook the pudding in.
Into the melted butter, stir in sifted flour, sugar, cocoa, milk, egg and vanilla. Mix together.
Combine the extra sugar and cocoa in a separate bowl and sprinkle over the top of the pudding mixture.
Pour over the hot water.
Cook in the microwave on high for 8 minutes (my microwave is 1100 watts. If yours is less, you may need to do it for a little longer).
You will know it is ready when the mixture is cake like and the chocolate sauce has thickened around the edges.
Serve the pudding into a bowl, coating the pudding with some of the chocolate sauce and a scoop of ice cream on the side.