Espresso-soaked ladyfingers layered with a cooked zabaglione-mascarpone filling lightened with whipped egg whites, not cream - the traditional Italian method, and safer than using raw yolks.
1.Whisk the egg yolks, sugar, and Marsala together in a heatproof bowl, then set over a pot of barely simmering water and whisk continuously for about 10 minutes until pale, thick, and doubled in volume (a zabaglione) - this cooks the yolks safely.
2.Remove from the heat and whisk in the mascarpone until smooth, then let cool slightly.
3.Beat the egg whites with a pinch of salt to stiff peaks, then gently fold them into the mascarpone mixture in two additions to keep it light.
4.Dip each ladyfinger briefly in the cooled coffee (mixed with a splash of Marsala if using) and layer half of them in a dish, then spread half the mascarpone mixture over the top; repeat with a second layer.
5.Chill for at least 6 hours, ideally overnight, then dust with cocoa powder before serving.