Preheat your oven to 180°C/gas mark 4/350°F.
Add your icing ingredients into a heavy-based saucepan and bring to the boil, to dissolve and melt. Make sure to turn off the heat once it starts boiling and then continually stir until you are left with a thick chocolatey glossy icing. Set aside to cool while you make the cake.
Line the bottom of your cake tin with grease proof paper. I use a square 20cmx20cm tin but I avoid the springform ones as they have a tendency to leak and this is a very wet batter.
To a bowl, add your flour, baking soda, salt and ground coffee and cocoa and mix together using your stand mixer, hand mixer or even a whisk.
In a separate bowl mix together both sugars, water, oil and vinegar, and then add this mixture to your flour mix. Combine using your mixer of choice. Pour this gooey chocolate cake batter into your baking tin and bake for 30 minutes. But check after about 25 minutes as the exact time will depend on your tin and oven. Be careful not to overcook as this will turn it from gooey and fudgy to dry. You’ll know it’s ready when a skewer comes out clean.
Let cool in its tin and when ready remove from the tin out onto a wire cooling rack.
Once both your cake and icing are cool, start putting it together. Give your icing a quick stir. Now how you add your icing is up to you. I like to drizzle it over but you can also pour it on and then spread with a spatula. Once you’ve iced your cake set aside and allow the icing to set.
Once set, cut your cake into brownie sized squares and enjoy.