How to Make It
In a small saucepan, combine 1 cup of the heavy cream with the gelatin over low heat, stirring constantly, until the gelatin dissolves. Let cool completely.
Fill a large bowl with ice water. In a medium stainless steel bowl, whisk the egg yolks with 1 cup of the sugar and the vanilla extract. Set the bowl over a pan filled with 1 inch of simmering water and cook over moderately low heat, whisking constantly, until the mixture is pale and thick and registers 160° on an instant-read thermometer, about 10 minutes. Set the bowl in the ice water and let the egg-yolk mixture cool, stirring occasionally.
In the bowl of a standing electric mixer fitted with the whisk attachment, beat the remaining 2 cups of heavy cream with the mascarpone and the remaining 2/3 cup of sugar at medium-high speed until soft peaks begin to form. Gradually add the cream-gelatin mixture and brandy and beat until firm peaks form. Using a rubber spatula, fold one-fourth of the whipped cream mixture into the cooled egg-yolk mixture, then fold it into the remaining whipped cream until no streaks remain. Scrape the semifreddo mixture into a 10-cup silicone kugelhopf mold or another 8- to 10-cup mold, spreading it in an even layer. Press plastic wrap directly onto the surface of the semifreddo and freeze for at least 24 hours, until very firm.
Carefully peel the mold from the semifreddo, shaking gently onto a platter. Cut into wedges and serve with the Stewed Winter Fruits in Spiced Wine Syrup.
The brandy-mascarpone semifreddo can be frozen, in its mold, for up to 2 weeks. At room temperature, the semifreddo will keep its shape for about 30 minutes.