Chocolate and espresso go together like peaches and cream or beer and pizza. You can have one without the other, but they're usually better together. There are a couple of reasons why the two are ...
Preheat the oven to 140°C and line a 9-inch tin with parchment. Melt the chocolate, butter, coffee and liqueur together in a heavy-based saucepan. Stir this mixture into the dry ingredients.