- Preheat oven to 180c/160c fan/gas4. Grease a 4cm deep rectangular tin 28cm x 19cm, and line with baking paper.
- Melt the butter in a small pan. Remove from heat and stir in the cocoa. leave to cool for 10 mins.
- Whisk the eggs, sugar and vanilla extract together in a large bowl until pale and foamy.
- Stir in the cocoa mixture, flour, baking powder and chilli powder. Pour mix into tin. Bake for 35mins or until top is firm and centre is still soft .
- Cool for 10 mins and then turn out onto a cooling wire. When cold cut into 16 squares and dust with icing suga