Zabaglione

Place the egg yolks and caster sugar in a large, deep, round-bottomed metal or glass bowl. Whisk vigorously by hand or with a hand mixer until the mixture turns pale ivory, triples slightly in volume, and falls from the whisk in a thick, slow ribbon that holds its shape on the surface for 2-3 seconds before dissolving. This pre-mixing — called 'blanchir' — begins the emulsification and ensures even, smooth cooking over the bain-marie. The sugar must be nearly fully dissolved before the bowl goes over heat — feel the mixture between fingers; it should feel smooth, not gritty.

Add the Marsala wine to the ribboned yolk-sugar mixture and whisk to combine. The mixture will thin out significantly — this is expected. The Marsala should be at room temperature; cold wine can cause the eggs to cook unevenly. Taste the raw mixture: it should be sweet, winey, and slightly rich. This is your baseline — everything that follows is just cooking and incorporating air.

Bring a saucepan of water to a gentle simmer — the water must not touch the bottom of the bowl, and it must not boil aggressively. Place the bowl of zabaglione base over the simmering water and immediately begin whisking continuously in a figure-eight pattern, making sure to reach the sides and bottom of the bowl. Whisk without stopping for 8-12 minutes. The mixture will slowly begin to thicken, increase dramatically in volume, and change from liquid to a thick foam. Watch the temperature: if you see any steam rising from the mixture or the eggs begin to look lumpy at the edges, remove the bowl from the heat immediately and continue whisking off-heat for 30 seconds, then return. The target temperature is 70-75 C (160-170 F). The zabaglione is done when it has tripled in volume and holds a soft mound.

Divide the warm zabaglione immediately among warm glasses or shallow coupes — it will begin to deflate and separate within 10-15 minutes, so speed matters. Spoon the fresh berries or sliced peaches alongside or beneath the foam. The warm foam against cold or room-temperature fruit is the defining contrast of the dish. Serve with a small spoon and a delicate biscuit such as a savoiardi or amaretto if desired. Zabaglione can also be chilled briefly and served cold, in which case fold in a small amount of softly whipped cream while it is still warm to stabilize the foam.