Pre-heat the oven to 150 C / 300 F.
Add the water, coffee (if using), butter and cocoa to the bowl and heat/melt for 3 minutes / 80 degrees / speed 2. Remove lid and allow to cool. (This will take around 10 minutes, ideally you want the temperature to drop to 50 degrees or below)
Meanwhile, grease and line two or three cake tins (see notes).
Once the mixture is cool, add the eggs and vanilla extract. Mix for 5 seconds / speed 4.
Add the sugars, flour, baking powder and bicarb soda. Mix for 30 seconds / speed 4.
Pour into cake tins (the batter is quite runny so you can pour directly from the TM bowl).
Bake in the oven for 30 minutes, or until a skewer inserted into the middle of the cake comes away clean.
Allow to cool for a couple of minutes in the tin before carefully turning out onto a wire rack to cool completely.