Step 1

Preheat oven to 180°C. Grease an 18 x 28cm cake tin with the melted butter or margarine and line the base of the pan with non-stick baking paper.

Step 2

Place butter, brown sugar and chocolate in a large saucepan and stir over medium heat until well combined (see microwave tip).

Step 3

Remove from heat and beat in the eggs using a wooden spoon.

Step 4

Sift together the flour, cocoa and baking powder into the chocolate mixture and stir until well combined. Stir in the walnuts.

Step 5

Pour into the prepared tin and bake in the preheated oven for 35-40 minutes or until firm and until a few crumbs cling to a skewer when it's inserted into the centre.