Heat oven to 170°C/150°C fan-forced. Grease a 23cm round springform pan with butter and line with baking paper.
To make the cake, place the butter, chocolate and hot coffee in a large heatproof bowl and mix well until everything is melted, combined and smooth. Whisk in sugar by hand until dissolved. Add eggs and vanilla extract and whisk again until thoroughly combined and smooth. Sift flour, cocoa powder and a pinch of fine salt together into a medium bowl, then whisk into the melted chocolate mixture until smooth. Batter will be liquid, but don’t think you’ve missed something; this is how it should be.
Pour batter into the prepared pan, tapping base of pan to remove air bubbles, and bake for 50 minutes-1 hour, until cake is cooked and a skewer inserted into the centre comes out clean or with just a few dry crumbs attached. The top will form a crust and crack a little, but don’t worry, this is expected. Leave the cake to cool on a wire rack for 20 minutes before removing from pan, then set aside on wire rack until completely cool.
Meanwhile, to make the chocolate ganache, place chocolate pieces in a food processor and whiz until fine. Set aside, keeping chocolate in food processor.
Combine cream and glucose syrup in a small saucepan and place over medium- high heat. As soon as bubbles begin to appear (just before it comes to a boil), remove from the heat.
Get the food processor running again, with the chocolate still inside, and pour in the hot cream in a steady stream. Process for 10 seconds, then add the butter. Continue to process until mixture is shiny and smooth. (You can also make the ganache by hand; just make sure the chocolate is chopped very finely before adding the cream mixture. Stir with a wooden spoon until almost melted, then add the butter. Stir again until the ganache is smooth.)
Use a rubber spatula to scrape the ganache into a bowl and cover with plastic wrap, with the plastic touching the surface of the ganache. Set aside for about 2 hours at room temperature until it has set to a spreading consistency. (Ganache can be stored at room temperature, providing it’s not too warm, for 3 days or kept in the fridge for up to 2 weeks. It can also be frozen, although it will lose a bit of its shine when defrosted.)
To make the espresso cinnamon mascarpone cream, place all ingredients in a stand mixer fitted with the whisk attachment. Beat for 1-2 minutes until soft peaks form.
Peel the baking paper from the cake and discard. Transfer cake to a serving platter and spread the ganache on top. Slice cake into wedges to serve, with a spoonful of the espresso cinnamon mascarpone cream alongside.
