Serves 4-6

Method

Place the egg yolks and caster sugar into a large mixing bowl and beat. (I use an electric hand whisk). Beat together until it looks very pale and thick. This usually takes a couple of minutes.
Add the mascarpone into the pale egg and sugar mixture. Beat on a slow speed. Initially it will look curdled, but keep beating until it is incorporated and smooth.
Place the egg whites into a medium bowl and whisk with clean beaters, until the egg white forms stiff peaks.
Gently fold the egg white into the mascarpone mixture and then set aside.
Put the espresso and Tia Maria together into a mug.
In a medium-sized glass serving bowl, place half of the sponge fingers at the bottom and spoon over half of the coffee mixture onto the sponge fingers.
Cover the sponge fingers with half of the mascarpone mixture and top that with half of the chocolate.
Repeat this whole process, layering the sponge fingers and spooning the remaining coffee mixture onto them. Cover with the remaining mascarpone mixture and sprinkle the remaining chopped chocolate on top. Sift the cocoa powder all over.
Place the dessert into the fridge for several hours until the dessert is set and chilled. It is better to leave it overnight if you can.
Serve the dessert straight from the fridge.

Tips

Make sure you use very good quality free range eggs.
I chop the chocolate in my food processor to minimise handling.
I make the espresso in my Nespresso machine using the Indriya capsule. This is an intense coffee with spicy notes, from India.
If I make this dessert for a dinner party, I just double all the ingredients and serve it in a large glass bowl for everyone to help themselves.
You can also make individual ones, in small glass bowls, or in large martini glasses.