Mix the egg yolks and sugar with the whisk of the hand mixer until creamy. Add mascarpone by the spoonful and stir until smooth. Halve the biscuits. Mix espresso and liqueur. Soak half of the biscuits in the liquid and put 4 halves each on the glass bottoms.
Pour half of the cream on the biscuits and smooth it down a bit. Spread the rest of the biscuits on top and soak with the remaining liquid. Spread the rest of the cream on the biscuits. Chill the tiramisu for at least 1 hour. Dust with cocoa shortly before serving
Waiting time approx. 1 hour