Peach Sabayon with Balsamic Peaches

3 medium peaches (1 lb total), halved, pitted, and each half cut into thin slices
2 teaspoons balsamic vinegar
1/4 cup sugar
4 large egg yolks
1/3 cup dry white wine
3 tablespoons peach brandy (use extra wine if no brandy)

Gently toss peaches with vinegar and 1 tablespoon sugar, then let macerate 30 minutes.

When peaches have macerated 15 minutes, combine yolks, wine, brandy, and remaining 3 tablespoons sugar in a large metal bowl set over a saucepan of barely simmering water and beat with a handheld electric mixer at medium-high speed until sabayon registers 140°F on thermometer, about 7 minutes. Continue beating over simmering water until sabayon has tripled in volume and forms a thick ribbon when beaters are lifted, about 4 minutes more. Remove bowl from saucepan.

Divide peaches and their juice among 4 bowls and top with sabayon.