- Pre-heat the oven to 180C, and line a 23cm x 23cm baking tin with baking parchment.
- Set a bowl over, but not touching, a pan of simmering water, and add 200g of the chocolate, broken into pieces. Allow to melt, stirring occasionally, and then remove from the heat immediately.
- Meanwhile, beat the butter and sugar together until light and fluffy, and break the rest of the chocolate into chips.
- With the mixer still running, gradually add the eggs, beating well between each addition to ensure it’s thoroughly incorporated before pouring in any more. Leave mixing on a high speed for five minutes until the batter has a silky sheen, and has increased in volume.
- Remove the bowl from the mixer, and gently fold in the melted chocolate and chocolate chips with a metal spoon, followed by the sifted flour, baking powder, salt, cocoa powder and walnuts.
- Spoon the mixture into the tin, and bake for 30 minutes. Test with a skewer; it should come out sticky, but not coated with raw mixture. If it does, put it back into the oven for another 3 minutes, then test again.
- When the brownies are ready, remove the tin from the oven and leave to cool for at least half an hour before cutting into squares. Store in an air-tight container; these will keep happily for a week (if they hang around that long).
You could add anything you like to these – marshmallows, broken biscuits, cherries, hazelnuts – it’s up to you. You could even try adding cardamom if you want something a bit different.