Pre-heat your oven to 180C/160C Fan/350F/Gas Mark 4 and line a muffin tray with cupcake cases
To make the cupcake sponges, start by creaming together the butter and caster sugar
Add the eggs and whisk them in one at a time, then mix in the cocoa powder and self raising flour
Seperate the mixture between 12 muffin cases
Bake the cupcakes for 20 minutes or until a skewer inserted comes out clean
To make the Nutella buttercream mix together the butter and icing sugar until smooth, then mix in the Nutella and the milk. Put it into a piping bag with a star nozzle and pipe it onto the cupcakes.
Top them with mini Bueno pieces and chocolate strand sprinkles