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Pour the half-and-half into a heavy saucepan. Place the vanilla bean on a work surface.
Using a small, sharp knife, cut the bean in half lengthwise. Using the knife tip,
scrape the seeds from the vanilla bean, then add the seeds and bean halves to the
half-and-half. Bring to a simmer over medium-high heat. Remove from the heat, cover and let stand for 30 minutes. Return the saucepan to the stovetop over medium-high heat and bring to a simmer.
Meanwhile, in a heatproof bowl, whisk together the sugar and egg yolks until blended.
Form a kitchen towel into a ring and place the bowl on top to prevent it from moving.
Gradually pour the hot half-and-half mixture into the yolk mixture, whisking constantly.
Return the mixture to the same saucepan and place over medium-low heat.
Cook, stirring constantly with a wooden spoon, until the custard is thick enough to coat
the back of the spoon and leaves a clear trail when a finger is drawn through it, about 5 minutes.
Do not allow the custard to boil. Pour the custard through a medium-mesh sieve set over a clean bowl. Refrigerate until cold, about 1 hour. Transfer the custard to an ice cream maker and freeze according to the manufacturer's