For the Cake:
Line a 23-25cm square or round cake tin with baking paper.
Pour the cocoa powder, dark brown sugar and boiling water into a mixing bowl and whisk together until well combined and set aside.
In another bowl mix together flour, bi-carb and baking powder and set aside
Place the butter, caster sugar and scraped vanilla bean into the bowl of a stand mixer fitted with a whisk attachment and whisk on high speed until pale and creamy.
Once pale add one egg and whisk again until combined followed by a little of the flour mix, then repeat with the other egg. Add the remaining flour mix a little at a time mixing well in between each addition.
Remove the bowl from the mixer and remove the whisk. Pour the cocoa powder and water mixture into the cake batter and whisk well to combine until the mixture is smooth and silky.
Pour the cake batter into the lined cake tin and set aside to rest for 10 minutes. Place the cake into a pre-heated oven combi setting 130°C for 35-45 minutes until cooked and a skewer inserted into the cake comes out cleanly.

For the Mirror Glaze:
Soak the gelatine leaves in a bowl of cold water for 8-10 minutes.
Place the cream into a small saucepan over medium heat on the stovetop and bring to the boil.
In another saucepan pour in the water and sugar and place it also on the stovetop over high heat and bring to the boil.
Once boiling remove the sugar mixture and add the cocoa powder to the pot and whisk well to combine. Remove the cream from the stovetop and add it to the cocoa powder mixture and whisk it in also until smooth.
Finally remove the soaked gelatine leaves from the water and squeeze out the excess water from the gelatine and add the leaves to the pot, whisk again to combine.
Pour the finished glaze into a bowl or jug and cover with clingfilm and chill in the fridge until required.

For the Mocha Cremeux:
Soak the gelatine leaves in a bowl of cold water for 8-10 minutes.
Pour milk, cream, sugar, coffee and egg yolks into a medium sized saucepan and place over medium heat stirring all the time until the mixture begins to thicken (approx 5-6 minutes)
Once the coffee mixture has thickened remove from the stovetop and pour the hot coffee mixture over the chocolate buttons and whisk until smooth.
Remove the gelatine leaves from the water and squeeze out excess water and add the leaves to the coffee/chocolate mix and whisk until combined.
Cover the cream with clingfilm and place in the fridge to chill until required.

Preparation:
Once the cake has baked remove it from the oven and while warm turn the cake out onto a cooling rack lined with baking paper.
Place the cake tin back on top of the cake with some baking trays to gently press the cake into a uniform shape. Leave the cake to cool for minimum of 3-4 hours.
Once completely cool cut the cake in half and spread over the mocha cremeux as evenly as possible and place the top of the cake back on pressing down to make the surface as even as possible.
Scrape away any excess cremeux and place the cake in the freezer for minimum of 30 minutes.
Remove the glaze from the fridge and place it covered in the oven steam setting 40°C until the mixture liquefies again (approx 40 minutes)
Once the glaze is ready and the cake semi frozen transfer the cake to a cooling rack over a baking tray and pour the warm glaze over the cold cake until the entire surface and sides of the cake are covered with glaze.
Leave the cake to rest on the bench for 5-10 minutes for the glaze to re-set then transfer the cake to a serving platter and garnish with some chocolate shavings and serve.