Add butter and chocolate buttons into four large mugs. Microwave for 40 seconds or until melted
Stir 1 tablespoon of sugar into the mug
In a bowl, beat the eggs and add to you mug.
Mix in the flour and Nutella to the centre of your mug.
Cook in the microwave for 1 minute (800 watts) until the tops of the cake has turned opaque.
Let it cool and serve with sprinkles (optional)
No chocolate buttons? use chocolate chips or a broken-up chocolate bar. No self-raising flour? Use plain and add a small amount of baking powder to each mug.