1. Preheat oven to 170C/340F. Add self-raising flour, cocoa powder and baking powder to a bowl.
2. Mix all of the dry ingredients together and set aside for later.
5. Add caster sugar to the butter and whisk for 5 minutes.
6. The butter and sugar mixture should be pale yellow.
7. Add one egg to the bowl and mix until the egg disappears. Repeat this step with the remaining eggs.
8. Add half of the flour mixture and milk to the bowl and whisk.
9. Add the remaining flour mixture to the batter and mix. Make sure you do not overmix the batter. There should still be some lumps
10. Pour an equal amount of batter into each tin and bake cakes in the preheated oven for 20-25 minutes. If the skewer comes out clean then the cake is done.
11. Safely remove the cakes from the oven and leave them to cool in the tins for 5 minutes.
12. Transfer the cakes to a cooling rack and leave to cool completely.
16. Add oreo crumbs to the bottom rim of the cake using a spoon.
17. Pour chocolate drip on top of the cake and down the sides to create a drip effect.
18. Once the frosting and the drip have set, add swirls of buttercream and oreos around the top of the cake. Then add more oreo crumbs to the middle.