Pre-heat the oven to turn the oven on to 180C/ 160C fan/ gas 4. Cut 185g unsalted butter into small cubes and tip into a medium bowl. Break 185g dark chocolate into small pieces and drop into the bowl. Either over a bane marie or in the microwave until the butter and chocolate has melted completely.

Using a shallow 20cm square tin, cut out a square of non-stick baking parchment to line the base. Tip 85g plain flour and 40g cocoa powder into a sieve held over a medium bowl. Tap and shake the sieve so they run through together and you get rid of any lumps.

Chop up the leftover chocolate into small chunks.

Break 3 large eggs into a large bowl and tip in 275g golden caster sugar. With an electric mixer on maximum speed, whisk the eggs and sugar. They will look thick and creamy, like a milk shake.

Pour the cooled chocolate mixture over the eggy mousse, then gently fold together with a rubber spatula until the two mixtures are one and the colour is a mottled dark brown.

Add the flour and cocoa powder to the eggy mixture then fold gently until combined. Add any chocolate chunks you want in the brownies.

Pour the mixture into the prepared tin, scraping every bit out of the bowl with the spatula. Gently ease the mixture into the corners of the tin and paddle the spatula from side to side across the top to level it.

Put in the oven and set your timer for 25 mins. When the buzzer goes, open the oven and all the extra chocolate to the top of the brownies and then put it back in the oven for 5 minutes.

Leave the whole thing in the tin until completely cold. Cut into squares.