Preheat the oven to 375°F, and line a 9x5-inch loaf pan by brushing with oil and adding a generous sheet of parchment paper to over hang on the sides (this helps remove it from the tin later), place it on a baking tray and set aside. You will also need a smaller tin to bake the extra batter, I like using a mini loaf tin or a 5/6 inch round tin.

In the boiling water add the cocoa powder and coffee powder, stir and set aside. In a small bowl add the flour, baking soda, salt and stir together, set aside.

In a large mixing bowl, cream the butter and sugar with an electric hand beater or whisk.

Add the eggs and vanilla, beating in well. Fold in the melted and cooled chocolate, blend well but be careful not to over beat, the ingredients should be just combined.

Alternate the dry ingredients and the boiling water, spoon by spoon, until you have a smooth and fairly liquid smooth batter.

Pour into the lined loaf pan 3/4th of the way - don't overfill the pan or it will overflow. Pour any excess into the other smaller tin and start testing for doneness at 20 minutes.

Bake the cake for 30 minutes at 375°F. Turn the oven down to 325° F and continue to cook for another 15 minutes.

The cake will still be a bit squidgy inside, so an inserted cake tester or skewer won't come out completely clean. Place the loaf pan on a rack, and leave to get completely cold before turning it out.