Ingredients

　　1 quart vanilla ice cream, softened

　　1 cup (about 8) finely chopped marrons glacés (candied chestnuts, available at specialty foods shops)

　　1 1/3 cups heavy cream

　　1/3 cup firmly packed dark brown sugar

　　6 ounces fine-quality bittersweet chocolate, chopped fine

　　1 ounce unsweetened chocolate, chopped fine

　　2 tablespoons unsalted butter

　　2 tablespoons Cognac, or to taste

　　In a bowl stir together well the ice cream and the marrons glacés and freeze the mixture, its surface covered with plastic wrap, for 2 to 3 hours, or until it is firm. In a heavy saucepan boil the cream, stirring occasionally, until it is reduced to about 1 cup, whisk in the brown sugar, and simmer the mixture, whisking, until the sugar is dissolved. Remove the pan from the heat, whisk in the chocolates, whisking the mixture until it is smooth, and whisk in the butter and the Cognac. Serve the sauce warm over the ice cream.