250g unsalted butter
200g dark chocolate ( at least 70% cocoa french dessert chocolate is perfect)
50g walnuts, roughly crushed (optional)
80g pure cocoa powder
65g plain flour
1 tsp baking powder
360g caster sugar
4 large free range eggs
Preheat the oven to 180c/350f/gas mark 4. Line a 25cm baking tray with greaseproof paper, or just butter it well. Melt the chocolate and butter together either in a bowl in a pan of boiling water, or in a microwave (this doesn't take long don't burn it). Add the nuts and stir it up. Mix the flour, baking powder, sugar and cocoa powder in a separate bowl, then add the butter and chocolate. Beat the eggs and mix them in.
Pour the mix into the baking tray and cook fro about 20 minutes. If you stick a knife in, you don't want it to come out clean like with a cake - they're nicer when they're gooey.