Tiramisu

Method

1. Before you start, take the mascarpone out of the fridge so it softens for about 20 minutes; slightly softened, it beats in smoothly. Make the espresso, stir in the marsala, if using, and pour it into a shallow dish to cool completely while you make the cream.
2. Separate the eggs, putting the whites in a spotless, grease-free bowl so they whip up well and the yolks in another. The eggs stay raw, so use pasteurised eggs if you are serving anyone pregnant, very young, elderly or unwell.
3. Whisk the yolks and sugar with an electric whisk for 3 to 4 minutes, until pale and thick enough to leave a trail. Add the mascarpone and beat on low speed, only until smooth and no streaks remain.
4. Wash and dry the beaters, then whisk the whites to soft peaks that droop at the tip. Stir a spoonful into the mascarpone to loosen it, then gently fold in the rest with a large metal spoon, keeping in as much air as you can.
5. Dip each savoiardi into the coffee for a count of one or two, turning it once, so it soaks at the edges but stays firm in the middle. Lay them in a single layer in a dish about 20 by 30cm, then spread over half the cream.
6. Repeat with a second layer of dipped savoiardi and the rest of the cream, smoothing the top. Cover and chill for at least 6 hours, ideally overnight, so the cream sets and the biscuits soften into cake.
7. Just before serving, dust the top thickly with cocoa through a fine sieve, so it stays dry and velvety. Cut into squares with a knife dipped in hot water and serve cold, on its own or with a small coffee.