Mix coffee with 2tbsp boiling water in a large jug
Add coffee liqueur and 75ml cold water
Pour into shallow dish
Beat mascarpone, condensed milk and vanilla extract with electric whisk until thick and smooth
Break sponge pieces into 2/3 pieces and soak in coffee mixture
Puta few pieces of sponge in the base of serving dish
Top with cream mixture
Sift cocoa over and chill for a couple of hours before serving