1 (4-inch) piece vanilla bean (or 1 1/2 teaspoons vanilla extract)
1 cup whole milk
2/3 cup granulated sugar, divided
2 cups heavy cream
1 large egg plus 2 egg yolks
Split the vanilla bean in half lengthwise, scraping both sides with a paring knife. Reserve both pod and scrapings. Combine the milk, 1/3 cup of the sugar, the heavy cream and reserved vanilla pod and scrapings in a heavy saucepan over medium-high heat. (If using vanilla extract, do NOT add it now.) Bring mixture to 175 F on an instant-read thermometer, stirring occasionally.
Meanwhile, combine the whole egg and egg yolks with remaining 1/3 cup sugar in a medium bowl and beat with an electric mixer, or whisk by hand, until pale yellow and thick, about 2 minutes with a mixer or 4 minutes by hand.
Remove 1/2 cup of hot milk mixture from saucepan and add slowly to beaten egg yolks while whisking vigorously. Whisk this mixture back into saucepan. Over low heat, cook and stir mixture until it thickens enough to coat back of a spoon (but do not let it boil) and reaches 170 to 180 F on a thermometer. Remember, custard should be thickness of heavy cream but should not boil or bubble because that will cause it to curdle
Strain custard through a fine-mesh strainer into a clean bowl sitting in an ice bath. Remove vanilla pod (if using) from strainer and add to custard. Cool, stirring occasionally so a skin doesn't form. When custard has cooled for about 20 minutes, remove from ice bath (if using vanilla extract, stir it into custard now), cover with plastic wrap, pressing down against surface to keep a skin from forming during its remaining time in refrigerator, and refrigerate until thoroughly chilled, at least 2 hours but up to 48 hours is OK.
When ready to proceed, pour custard into freezer container and follow manufacturer directions. Makes about 1 quart.
VARIATIONS: Add 3 ounces chopped, semisweet chocolate (or chocolate chips) about 1 minute before churning is completed; add 1 cup coarsely crumbled Oreo cookies about 1 minute before churning is completed; stir 3 tablespoons instant coffee or espresso powder into milk mixture before heating. For chocolate ice cream, increase sugar to 1 cup, adding 3/4 cup to milk mixture and remaining to eggs; beat 1/3 cup unsweetened cocoa powder into whipped egg mixture.
— Recipe adapted from "The Dessert Bible," by Christopher Kimball.