Bake the Cake:

1. Preheat the oven to 170 deg C/150 deg C/Gas Mark 3. Grease a round cake tin of diameter 23 cm and line with baking parchment and leave it to one side ready for later to fill with cake batter.
2. Dice the butter into 2 cm cubes and chop the dark chocolate into pieces of 2 cm so they can dissolve easily. Lightly beat the eggs and set aside. Combine butter, dark chocolate and hot coffee in a large bowl and mix well. Add the sugar and whisk well until dissolved. Whisk the vanilla extract and lightly beaten eggs into this same bowl until well combined and smooth.
3. In a separate bowl sift the flour, cocoa powder and salt , combine well.
4. Add the dry ingredients from step 3 into the bowl of wet ingredients. The batter will appear very liquid like but do not worry as the recipe expects it to be so.
5. Pour the cake mixture into the cake tin that was prepped in Step 1 and bake for about 60 minutes or until a skewer inserted comes out clean. There might be few cracks on the crust of the cake but again this is normal and let the cake cool down for 20-30 minutes before turning it out of the tin.

Make the Gananche:

1. Blitz the dark chocolate into fine powder in a food processor. Do not detach food processor as the next step happens in the food processor itself. If you don't have a food processor then you can do this in a bowl with help of wooden spatula.
2. Place a small pan over medium high heat and pour double cream + golden syrup, heat this mixture till you see light bubbles appear on the walls of the pan. Turn it off before it reaches a boil and take it off the heat immediately.
3. Take the hot mixture from step 2 and pour into the running food processor in a steady stream, then add the butter and process until well combined and smooth.
4. Set this mixture aside in a bowl covered with a clingfilm actually touching the top of the mixture. This can be poured over the cake when liquid to achieve a shiny coating.  You can leave this until it has reached the consistency you like and then use it to ice the cake. Ideally leave it for 2 hours for a thicker consistency