Melt the chocolate in a large bowl suspended over hot, but not boiling water along with the butter.
Once melted mix in the sugar.
Beat in the eggs until the mixture is thick and glossy.
Sift in the flour and cocoa then fold in.
Stir in the chocolate beer as carefully as you can.
Pour into a 22 cm (9") sq silicon cake mould or lined tin and bake at 180℃ (350℉, Gas 4) for 20 mins. Or until the top is risen and crackly, but there's still a slight wobble in the middle of the bake.
Leave to cool then cut into 16 squares.
Notes
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.