I'm not a fan of using raw eggs in dishes. Can I leave out the egg and perhaps use some full fat whipping cream as extra liquid?
The risk of salmonella in raw or lightly cooked eggs can be a problem for some, particularly the very young, the elderly, pregnant women and those with a weakened immune system. Tiramisu often uses a combination of egg yolks and whisked egg whites with mascarpone to add richness (yolks) and lightness (whites) to the cream mixture.
If you can find carton egg whites in a supermarket, usually in the chilled section, then these can be useful as they are usually pasteurized and so should be safe to eat (but please check the packaging). In the UK the Two Chicks egg whites are available in some supermarkets and in the US there are several brands of carton egg whites. You could use these to replace the egg whites in the recipe and omit the egg yolks from the recipe. We would particularly suggest Nigella's Tiramisini recipe (from Nigellissima and also on the Nigella website) if you do use pasteurized egg whites as it follwos this route.
If you can't find pasteurized egg whites then you could use the Tiramisini recipe and use 120ml/1/2 cup double/heavy cream instead. Whip the cream to soft peaks before folding it into the mascarpone mixture. The mixture will not be as light as a traditional tiramisu but in the smaller Tiramisini portions it should still be delicious.