Pre-heat the oven to 170°C (325°F) and prepare an 8 x 8 inch tin by lining it with grease-proof paper or by greasing.
Slowly heat the chocolate and butter in a pan until just melted, then add the coffee. Remove from the heat, and leave to rest for a short while.
In a large bowl, whisk the sugar with the eggs, then add in the vanilla and chocolate mixture.
Sift the flour and cocoa together and stir into the wet ingredients, just until combined.
Pour into the tin and bake for around 20-25 minutes (until an inserted skewer comes out clean).
Remove from the oven and allow to cool completely. If you have the time, let the brownie sit in the fridge over night.