Preheat the oven to 180C (160C Fan) and line a brownie tin with baking paper.
Whisk the sugar and eggs together. As they are whisking melt together the chocolate and butter in 20 second bursts, stirring in between, until they are both completely melted. If you don’t have stand mixer, melt the chocolate and butter together first, once it is completely melted leave to one side and whisk together the sugar and eggs. The eggs should have doubled in volume.
Pour the chocolate mixture, vanilla into the egg mixture and fold together. You need to be gentle during the stage because you don’t want to knock all the air out of your eggs.
Add in the flour, cocoa powder and fold again until they are all completely incorporated
Finally add in the chocolate chips and your frozen mini crème eggs and fold through until they are evenly distributed.
Pour the mixture into your brownie tin and bake in the oven for 30-35 minutes. You will know they are ready because they will have a slight wobble.
Leave to cool completely in the tin.