Sabayon (called zabaglione in Italy) can be served over cake, ice cream, or fruit; it is a lovely way to dress up a simple white cake.
Put yolks, sugar, and Champagne in the heatproof bowl of an electric mixer set over a pan of simmering water. Whisk until hot and thick, 3 to 4 minutes. Attach bowl to mixer fitted with the whisk attachment. Beat on high speed until cooled and tripled in volume, about 5 minutes.