250g/9oz cooked and peeled beetroot
135g/5oz plain flour
1 heaped tsp baking powder
190g/6陆oz golden caster sugar
3 tbsp cocoa powder
200g/7oz dark chocolate (70% cocoa solids)
200g/7oz butter, plus extra for greasing
cr猫me fra卯che or double cream, to serve
5 free-range eggs, separated
4 tbsp hot espresso