Preparation

• In a medium saucepan, mix 1 cup of the cream with the milk, sugar, and a pinch of salt. Warm the cream mixture over medium-high heat, stirring occasionally, until the sugar dissolves and tiny bubbles begin to form around the edge of the pan, 3 to 4 minutes.
• Prepare an ice bath by filling a large bowl with several inches of ice water. Set a smaller metal bowl (one that holds at least 1-1/2 quarts) in the ice water. Pour the remaining cup of cream into the inner bowl (this helps the custard cool quicker when you pour it in later). Set a fine strainer on top. Whisk the egg yolks in a medium bowl.
• In a steady stream, pour half of the warm cream mixture into the egg yolks, whisking constantly to prevent the eggs from curdling.
• Pour the egg mixture back into the saucepan and cook over low heat, stirring constantly and scraping the bottom with a heatproof rubber spatula until the custard thickens slightly (it should be thick enough to coat the spatula and hold a line drawn through it with a finger), 4 to 8 minutes. An instant-read thermometer should read 175° to 180°F at this point. Don’t let the sauce overheat or boil, or it will curdle. Immediately strain the custard into the cold cream in the ice bath.
• Cool the custard to below 70°F by stirring it over the ice bath. Stir the peach puree and mascarpone into the cooled custard.
• Refrigerate the custard until completely chilled, at least 4 hours. Then freeze the custard in your ice cream maker according to the manufacturer’s instructions. Transfer the just-churned ice cream to an air-tight container, and freeze for at least 4 hours or up to 2 weeks.