Preheat the oven to 170°C.
Grease and line a small rectangular tin, about 15x15 cm.
Melt the butter in a pan. Cool for 5 minutes then stir in the cocoa. Set aside.
In a mixing bowl, whisk the eggs & sugar together until frothy, then add the vanilla. Stir in the egg& cocoa mixture, then the flour and finally the chilli flakes.
Transfer the mixture into the tin and bake for approx. 25-30 minutes. The middle should be bit sticky.
Let the cake cool completely, then cut it into squares.
Dust with icing sugar before serving.