Heat the oven to 170°C/150°C (fan)/Gas 3½. Grease and line a 20cm cake tray with parchment paper.

In a saucepan melt the butter and chocolate together over a low heat. Take your time as to not burn the chocolate (See note). Allow the butter and chocolate mix to cool.

In a separate bowl whisk together the sugars, eggs and vanilla until pale and fluffy. This is where the key to a good brownie is. Ensure that the eggs and sugar get a really good whisk to incorporate lots of air. Add the chocolate and mix through.

Sift in the flour and cocoa and mix until well incorporated. Add to your lined tin and bake for 20-25 minutes.

The mix will still seem slightly undercooked but will continue cooking as you cool. Allow the mix to cool completely before taking out of the tin. You can speed this up by putting in the fridge.

Take out onto the chopping board and cut into squares. Dust with icing sugar and serve with Chantilly Cream, Ice Cream or fresh custard.