准备

做糖浆：

• 在2夸脱的重型锅中，将浆果，玉米糖浆，柠檬汁和肉桂混合在一起。将锅放在低火上，将浆果用土豆泥或大叉子捣碎。将热量提高到中低，并将混合物带到小火中。煮5分钟，偶尔搅拌，然后冷却5至10分钟。
• Put the berries in a fine sieve set over a bowl. Press on the berries to extract all the liquid; discard the solids. You’ll have about 1 cup liquid.
• In a separate bowl, beat the egg white just enough to loosen and break it up, but try to incorporate as little air as possible. Stir the beaten white into the blueberry syrup just until well combined, cover with plastic wrap, and refrigerate until thoroughly chilled. You can make the syrup up to three days ahead of making the ice cream.

使蛋ust：

• In a 1- to 2-quart heavy-based saucepan, heat the half-and-half over medium heat. Bring just to a boil, watching so it doesn’t boil over, and then remove it from the heat.
• Meanwhile, in a medium bowl, lightly beat the yolks to break them up. Whisk in the sugar just until incorporated. Don’t overwhisk; you don’t want a very thick, pale mixture. Set the bowl on a damp towel to hold it steady and very slowly pour the hot half-and-half over the egg mixture, whisking constantly so the yolks don’t curdle. Rinse the saucepan but don’t dry the inside; a film of water helps prevent the custard from sticking to the pot. Have ready a fine sieve set over a bowl. Return the custard to the saucepan and set it over medium-low heat. Stirring constantly with a wooden spoon, cook the custard until it thickens enough to coat the back of the spoon, 7 to 10 min.; a finger drawn across the back of the spoon should leave a clean trail. Immediately pour the custard through the sieve. Stir in the cream and the vanilla extract and press a piece of plastic onto the surface of the warm custard to keep a skin from forming. Poke a few slits in the plastic with the tip of a paring knife to let the steam escape. Let cool slightly and then refrigerate until well chilled, at least 4 hours but ideally 8 hours or overnight.

Make the ice cream:

• Stir the blueberry syrup into the chilled custard; mix thoroughly. Pour the mixture into an ice-cream maker and freeze following the manufacturer’s instructions. For the most intense flavor, serve right away. Otherwise, store in an airtight container for up to a week; let the ice cream soften in the refrigerator for 10 minutes before serving to coax out more flavor.