1. Preheat oven to 190C / 180C Fan Oven
2. Cream sugar and margarine together until smooth.
3. Beat eggs.
4. Sieve flour, baking powder and cocoa into a separate bowl.
5. Add half the eggs and a third of the flour mix into the margarine and sugar and blend together until smooth.
6. Add the remaining eggs and some more flour. Blend again.
7. Finally, fold in the last of the flour mix and blend until smooth.
8. Line muffin tin with bun cases and place a mini oreo in each.
   
9. Spoon the mixture into the bun cases.
10. Cook for 15 minutes.
11. Cool on a wire tray.
12. Pipe buttercream in a spiral at the top of each cup cake and place a mini Oreo on the top of each.

For the buttercream icing

You will need

1. 140g margarine
2. 280g icing sugar
3. 1-2 tbsp water
4. 1 tsp vanilla extract

Instructions

1. Beat the margarine until soft. Add half of the icing sugar and beat until smooth.

2. Add the rest of the icing sugar, vanilla extract and one tablespoon of water and beat the mixture until creamy and smooth. Add more water if necessary.