Preheat the oven at 220°C.
Grease and line a 20cm round spring-form cake pan's base with non-stick baking paper.
Melt the chocolate with the golden syrup and butter in a bowl over a saucepan of gently simmering water.
Set aside to slightly cool.
Place eggs and sugar in a large bowl and beat on high for 10 minutes with an electric hand beater until mixture is very thick and pale.
Fold in the flour gently then fold in the chocolate mixture until combined.
Pour into the cake pan and
bake on the center shelf for about 12 minutes.
Remove the pan from oven and stick a knife around the edge of the cake.
Remove collar from the cake pan and transfer the cake to the fridge for 1 hour to cool (this step is so important to set the middle of the cake).
Meanwhile, make the coffee mascarpone, by dissolving coffee in 1 tbsp of boiling water and set aside to cool.
Beat together the mascarpone, the coffee and the sugar in a bowl until stiff.
To make a chocolate leaf for decoration, brush a non-toxic leaf with the melted chocolate and peel the leaf off when cool.
Slice the cake.
Serve with a dollop of coffee mascarpone on top of each slice, a chocolate leaf on top and a scoop of sorbet on the side.