Put the egg and caster sugar in a bowl and mix until creamy.
Add the mascarpone and fold through the mixture
Stir the coffee (we recommend Jasper’s Juliet) in a bowl with the coffee liqueur. Dip the biscuits for a second or two in the coffee mixture, flipping them over to cover both sides. They should absorb just enough to keep firm but not fall apart.
Break the biscuits in half and line the bottom of 4 small glasses, alternating layers of mascarpone with layers of biscuit.
Dust the top with cocoa powder and chill your tiramisu in the fridge overnight.
