Line the inside of a 23cm (8-inch) square pan with foil so that is goes up the sides to the rim. Lightly grease with butter or non-stick cooking spray. Set aside.

Place 85g salted butter into a saucepan and place on a very low heat. Place 225g dark chocolate, broken into pieces over the butter. Stir until smooth.

Remove from the heat and stir in 150g (¾ cup) sugar. Beat in 2 eggs, one at a time.

Sift together 1tbs unsweetened cocoa powder and 3 tbs cornstarch and stir into the chocolate mixture.

Now beat the batter vigorously for at least one minute, until the batter is no longer grainy and nearly smooth, It will pull away from the sides of the pan.

Stir in 1/3 cup (65g) nuts, toasted and coarsely chopped.

Bake at 180c for 20-25 minutes till the brownies feel just set. Remove from the oven and let cool completely before removing from the pan and slicing into pieces.