Best Ever Brownies

Cut the butter into small cubes and set into a large bowl. Break the chocolate into small pieces and drop into the bowl. Fill a small saucepan about a quarter full with hot water, then sit the bowl on top and let butter and chocolate melt in double boiler. Put over a low heat until the butter and chocolate have melted, stirring occasionally to mix them. Now remove the bowl from the pan, and leave the melted mixture to cool to room temperature.

Preheat oven to 160C/ 180F/gas 4.

Line the base of a square tin.

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 for at least 8 minutes until they look pale and creamy: it will have tripled in volume.

Pour the cooled chocolate mixture over the eggy mousse, then gently fold together with a silicone spatula, going under and over in a figure of eight. Sprinkle flour, salt and cocoa powder into the mixture, and mix until you get rid of any lumps, using the same figure of eight action as before, adding the walnuts at the end.

Scrape the batter into the lined tin. Put in the oven for 25 minutes, or until just set in the center. If the brownie wobbles in the middle, bake for another 5 minutes. Take out of the oven, let cool, then cut into squares or triangles.