beat egg yolks with sugar on high speed for c.3 mins, til forms light, pale mousse.
In lge separate bowl stir mascarpone to soften, then gradually beat in egg-yolk mixture. Between each addition beat well. Then wash and dry whisk.
In a third separate bowl, whisk the egg whites until they form soft peaks. Fold them into the mascarpone mixture and put the bowl to one side.
Mix coffee and rum and dip sponge fingers briefly into it.
I make this in a large rectangular dish: Tiramisu tastes fantastic, but doesn't look great. If you must you can make it in cocktail glasses.
Layer the sponge fingers, followed by mascarpone mix, then chopped choc. Then repeat. Finish with dusting of cocoa powder.
Cover with cling film and chill for several hours.
This is my favourite dessert ever, and I am starving now!