Makes About 1 Quart
Two teaspoons of vanilla extract can be substituted for the vanilla bean; stir the extract into the cold custard in step 3. An instant-read thermometer is critical for the best results. Using a prechilled metal baking pan and working quickly in step 4 will help prevent melting and refreshing of the ice cream and will speed the hardening process. If using a canister-style ice-cream machine, be sure to freeze the empty canister at least 24 hours and preferably 48 hours before churning. For self-refrigerating ice-cream machines, prechill the canister by running the machine for 5 to 10 minutes before pouring in the custard.
1 vanilla bean
1 3/4 cups heavy cream
1 1/4 cups whole milk
1/2 cup plus 2 tablespoons sugar
1/2 cup light corn syrup
1/4 teaspoon salt
6 large eggs
Place 8-or9-inch-square metal baking pan in freezer. Cut vanilla bean in half lengthwise. Using tip of paring knife, scrape out vanilla seeds. Combine vanilla bean, seeds, cream, milk, 1/4 cup plus 2 tablespoons sugar, corn syrup, and salt in medium saucepan. Heat over medium-high heat, stirring occasionally, until mixture is steaming steadily and registers 175 degrees, 5 to 10 minutes. Remove saucepan from heat.
While cream mixture heats, whisk yolks and remaining 1/4 cup sugar in bowl until smooth, about 30 seconds. Slowly whisk 1 cup heated cream mixture into egg yolk mixture. Return mixture to saucepan and cook over medium-low heat, stirring constantly, until mixture thickens and registers 180 degrees, 7 to 14 minutes. Immediately pour custard into large bowl and let cool until no longer steaming, 10 to 20 minutes. Transfer 1 cup custard to small bowl. Cover both bowls with plastic wrap. Place large bowl in refrigerator and small bowl in freezer and cool completely, at least 4 hours and up to 24 hours. (Small bowl of custard will freeze solid.)
Remove custards from refrigerator and freezer. Scrape frozen custard from small bowl into large bowl of custard. Stir occasionally until frozen custard has fully dissolved. Strain custard through fine-mesh strainer and transfer to ice-cream machine. Churn until mixture resembles thick soft-serve ice cream and registers about 21 degree, 15 to 25 minutes. Transfer ice cream to frozen baking pan and press plastic on surface. Rreturn to freezer until firm around edges, about 1 hour.
Transfer ice cream to airtight container, pressing firmly to remove any air pockets, and freeze until firm, at least 2 hours. Serve. (Ice cream can be stored up to 5 days.)