Step 1

Chill the ice cream bowl: If your ice cream machine has a bowl that needs to be frozen before churning, put it in the freezer the night before you plan to make ice cream. (If you forget, you can make the base and refrigerate it overnight while the bowl is freezing, and churn the ice cream the next day.)

Step 2

Prepare an ice bath: Fill a large bowl with ice cubes and some water. Place another smaller bowl on top of the water, and place a fine-mesh strainer inside. Keep this close by while you make the ice cream base.

Step 3

Whisk the yolks and sugar together: Place 4 egg yolks and 2/3 cup granulated sugar in a medium bowl and whisk until combined. At first the mixture will be very thick and dark yellow, then it will smooth out and lighten to a pale lemon-yellow color.

Step 4

Warm the milk: Pour 1 1/2 cups milk into a medium saucepan and place over medium heat. Split 1 vanilla bean lengthwise, scrape the seeds into the milk, and add the pod (or just add 1 teaspoon vanilla extract). Bring the milk to a simmer, then remove from heat.

Step 5

Temper the egg-sugar mixture: Ladle out about 1 cup of the hot milk (no need to be exact). While whisking constantly, slowly pour it into the egg-sugar mixture. This warms the eggs and prevents them from curdling in the next step, and it's known as tempering.

Step 6

Add the tempered egg-sugar mixture: Slowly pour the tempered egg-sugar mixture into the saucepan with the remaining milk.

Step 7

Cook the ice cream base until thickened: Return the saucepan to low heat. Stir the mixture slowly, but constantly, scraping the bottom and sides of the pot. Keep cooking until the base has thickened enough to coat the back of the spatula and registers 170°F with an instant-read thermometer.

Step 8

Strain the ice cream base: Pour the base through the reserved fine-mesh strainer set over the bowl to remove the vanilla pod and any bits of egg that may have accidentally curdled. Remove the strainer, making sure to scrape any base that clings to the underside of the strainer off into the rest of the base.

Step 9

Add the cream: Stir 1 1/2 cups heavy cream into the ice cream base.

Step 10

Chill completely: Leave the ice cream base over the ice water bath, stirring occasionally, until completely chilled, about 20 minutes. Alternatively, cover the bowl and refrigerate for at least 3 hours or up to overnight.

Step 11

Churn the ice cream base: Transfer the ice cream base to the bowl of your ice cream machine. Churn until the base has thickened to a consistency somewhere between a very thick milkshake and soft-serve ice cream. In most ice cream makers, this takes about 20 minutes — check the instructions for your particular machine.

Step 12

Freeze the ice cream until solid: Transfer the churned ice cream to a freezer container. Press a piece of wax paper against the surface of the ice cream to prevent ice crystals from forming. Freeze until solid, at least 4 hours.