Line the base of a small pudding tin with baking paper and reserve an extra piece to cover the top.
Half fill a large saucepan with water and place over a medium/high heat - bring it to the boil.
Sift the self raising flour and cocoa into a small bowl and set aside until needed.
Place the softened butter and caster sugar in the bowl of an electric mixer and combine until pale and fluffy.
Add the egg and vanilla essence and combine well.
Add the milk and sifted flour/cocoa to the mixture alternatively and mix until combined.
Spoon the mixture into the pudding tin and place the extra piece of baking paper over the top before putting on the lid.
Carefully place the pudding tin in the saucepan of boiling water before reducing the heat so that the water is simmering and cover with the saucepan lid.
Allow the pudding to cook for 1 1/2 hours, don't forget to keep an eye on the water level and top up as needed.
Carefully remove the pudding tin from the saucepan before leaving to cool in tin for 5 minutes.
Carefully turn pudding onto a plate, before cutting into slices and serve with custard or ice cream - YUM!