Heat oven to 350 degrees Fahrenheit. Grease a 9-inch round springform pan with butter and line with parchment paper, then set aside.

Make the cake:

Place 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 salt together into a bowl and then whisk this into the melted chocolate mixture. The batter is liquid, but  this is how it should be.

Pour batter into the prepared pan and bake for 1 hour, or until the cake is cooked and a skewer inserted into the center 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 for 20 minutes before removing from the pan, then set aside until completely cool.

Make the chocolate ganache, if desired:

Place chocolate pieces in a small nicrowaveable bowl and set aside.

Combine cream and corn syrup in a small pan and place over medium-high heat. As soon as bubbles begin to appear (just before it comes to a boil), remove from the heat. (I also do this is a microwave by heating for about 2 minutes on power level 7. You must watch this closely or the cream may boil over.

Pour in the hot cream over the chocolate and whisk until smooth. You can blast this in the microwave for no more than 20 seconds at a time if the cream hasn’t melted the chocolate. Whisk well at all times. Process for 10 seconds, then add 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 fairly 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 actually touching the top of the ganache. Set aside until it has set to the consistency you want. I set this outside in the cold for about 20 minutes. Whisk it well to see if it is the consistency you want. If it isn’t, chill longer.   (The 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.)

Make the espresso cinnamon mascarpone cream, if desired: Place all the ingredients in the bowl of an electric mixer fitted with the whisk attachment. Beat for 1 to 2 minutes, until soft peaks form.

Peel the parchment from the cake and discard. Transfer to a serving platter and spread the ganache, if using, on top of the cake. Slice into wedges, divide the cake among plates and, if using, spoon the mascarpone cream alongside. With or without icing, the cake will keep well for up to 8 days in an airtight container or sealed well with plastic wrap.