• Preheat the oven to 325ºF or 160ºC. (for fan oven 320ºF & 150ºC) and line a 9 x 9 square pan with some baking parchment or greaseproof paper.

Mixing the brownie batter

• Melt the butter and the chocolate together in a bowl set over a simmering pan of water or in the microwave on medium setting, in 30-second intervals. Be sure to stir between each interval.
• While the chocolate and butter are melting, place the eggs and sugar in the bowl of an electric mixer fitted with the whisk attachment. Whisk on high until fluffy and pale in color. You can use an electric hand whisk if you don't have a stand mixer.
• Once the chocolate and butter are melted and the eggs are whisked, gently pour the chocolate mixture into the eggs. Use a hand whisk to gently fold the two mixtures together.

Baking brownies and checking for doneness

• Once the chocolate is incorporated, sieve the cocoa powder and flour into the chocolate mixture and fold in until just combined. Pour the brownie batter into the prepared baking tin and bake in the preheated oven for about 15 minutes. Turn the pan around and bake for another 10-15 minutes. *Be careful to not overbake.
• Once the brownies are baked, the top will be shiny and crackly and will appear set. Remove the brownies from the oven and leave them to cool in the tin for at least 1 hour before slicing them into squares.