Strawberry tiramisu with Marsala

• 4 eggs, separated
• 4 tablespoons sugar (see note)
• zest of 1

Hull the strawberries, then cut into quarters and place in a bowl. Dress with the lemon juice, Marsala and sugar. Cover and leave to macerate for at least 2 hours — or better still, overnight in the fridge — until the strawberries are sitting in a pool of sweet, slightly tangy crimson liquid. Strain the strawberry liquid into a deep dish large enough to roll the biscuits in, and set the strawbe