Make the espresso or strong coffee and stir in the sugar while it is warm. Allow it to cool completely. Add the Marsala, if using.
Place the mascarpone, double cream, icing sugar, and vanilla in a bowl. Whisk until the mixture is thick, smooth, and firm enough to pipe. (If using Marsala, add it towards the end and mix until combined.) Transfer the mascarpone cream to a piping bag fitted with a plain or star-shaped nozzle.
Transfer the chocolate spread to a piping bag. Snip a small hole in the tip of the bag.
Dip two ladyfinger biscuits into the cold coffee, turning them quickly so they are moist but still hold their shape.
Pipe a thin line of chocolate along one side of one biscuit. Pipe a generous line of mascarpone cream next to it. Press the two biscuits together with the chocolate and mascarpone in between, creating a small sandwich.
Place the pair of biscuits into an individual paper cupcake case. Repeat the process with the remaining ladyfinger biscuits.
To decorate, pipe a generous swirl of mascarpone cream on top of each tiramisu cake. Dust lightly with cocoa powder.
Finish with a few toasted, chopped hazelnuts or pistachios and a small piece of fresh fruit. Place the cakes in the fridge for a few hours, or overnight if possible.