Ingredients
225g butter, at room temp 
225g sugar 
4 eggs 
200g self raising flour 
25g cocoa powder 
1 tsp baking powder 
240g Oreos 
250g mascarpone 
300ml double cream 
½ vanilla extract or bean paste 
2 tbsp icing sugar 

Equipment needed 
2 x 20/23cm cake tin (if you only have one then bake half the mix and cover the remaining batter and when the cake is cooked and has cooled for 5 minutes, reline the tin and cook the second half of the batter)

Method
Grease and line your tins by buttering the base and sides and cover the bottom in greaseproof paper.  I don’t cut in a circle I just  fold it around and tuck it in. 

Preheat the oven to 180c. 

Take half of the Oreos and chop into smallish pieces, I like to do some very small with a few slightly bigger chunks. 

Beat your eggs. 

Take your butter and put into a large mixing bowl and beat until soft and smooth.  Add the sugar and beat them together until light and fluffy. Add a little egg mixture and beat then some more egg and beat again.  Repeat until all of your egg mixture is used up.  It could be at some point that this looks curdled - don’t worry if that happens, it will come together and will bake perfectly. 

Add the flour, cocoa powder and baking powder and gently mix the flour through. 

Add the chopped Oreos and gently mix through.  If your batter looks a bit stiff then add 1-2 tbsps of milk to slacken it a little. 

Put into the tins and cook for 20-25 minutes until cooked soft, slightly springy and cooked through.

Once completely cool make your icing by taking the other half of the Oreos and chopping them exactly as you did before. 

Put the mascarpone into a large bowl and beat until soft.  Add the icing sugar and mix through.  Add all of the vanilla and the cream a little bit at a time mixing until it thickens.  The cream should be thick but not stiff.  Fold through the Oreos through if the icing is a little thick then add 1-2 tbsps of milk. 

Take your nicest cake and keep for the top.  Put the bottom cake down on a plate and top with half of the mixture.  Put the top cake down and top with the remaining icing.