This recipe is great but I cheat using a ready made flan base, but you can use Sponge fingers instead. However the flan base looks better for presentation and saves time.
Add all of the sauce ingredients together, stir well and set aside to cool.
Combine mascarpone cheese, sugar, rum, vanilla in a mixing bowl. Using an electric mixer mascarpone mix in a mixer and add cream in gradually until stiff peaks form.
Pour the cooled sauce onto Flan base evenly and when absorbed spoon filling on top. Even out and smoothen, then make spikes with a spoon. Then evenly sieve cocoa powder on top.