Zabaglione (zabaione in Piedmontese) is the great egg-and-wine custard of Turin—a warm, frothy, intensely rich foam of egg yolks, sugar, and Marsala wine (or, in the original Piedmontese tradition, Moscato d'Asti) whisked over gentle heat until it billows into a golden cloud of extraordinary lightness and warmth. The dish is among the oldest documented Italian desserts, with references dating to the 16th century, and its creation is attributed (with varying credibility) to the Franciscan monk San Pasquale Baylon, patron saint of cooks. The technique is simple but demanding: egg yolks and sugar are whisked together until pale and thick (the yolks should 'ribbon'), then transferred to a round-bottomed copper bowl set over simmering water (a bagnomaria). Marsala wine is added—traditionally one half-eggshell measure per yolk—and the mixture is whisked continuously and vigorously over the gentle steam heat. The whisking incorporates air while the heat cooks the egg proteins, and over 8-12 minutes the mixture transforms from liquid gold into a billowing, foamy custard that triples in volume. The moment the zabaglione reaches the proper consistency—thick enough to hold soft peaks but still pourable—it is removed from heat and served immediately in warm glasses or cups. Delay is fatal: the foam deflates within minutes and the magic is lost. The warmth of the custard is part of the experience—zabaglione is not a cold dessert. It is served alone, over fresh berries, alongside dry biscuits (savoiardi or lingua di gatto), or spooned into glasses with crumbled amaretti. Some versions use Moscato d'Asti instead of Marsala, producing a lighter, more floral result more faithful to the Piedmontese origin. The dish is also used as a sauce for other desserts, a filling for pastries, and, when frozen, as the base for semifreddo allo zabaione.
Whisk yolks and sugar until pale and ribboning. Add Marsala (or Moscato). Whisk continuously over bagnomaria until tripled in volume. Remove at soft-peak consistency. Serve immediately—delay deflates it. Warmth is essential.
A copper bowl conducts heat more evenly and helps stabilize the foam. The water in the bagnomaria should simmer, never boil. Count 10 minutes of continuous whisking as your guide. A balloon whisk creates more volume than a flat whisk. Add a pinch of salt to the yolks before whisking to help break down the proteins.
Scrambling the eggs (heat too high). Under-whisking (doesn't achieve volume). Letting it sit after making (deflates). Using too much sugar. Not using a bagnomaria (direct heat scrambles the eggs). Serving cold.
Pellegrino Artusi, La Scienza in Cucina; Giovanni Goria, La Cucina del Piemonte