The Preparation
Combine the half-and-half and heavy cream in a medium saucepan over medium heat. Bring just to a simmer, stirring occasionally, then remove from heat.
In a large bowl, whisk the egg yolks until they lighten slightly in color. Gradually whisk in the sugar until combined.
Temper the eggs: Slowly pour a small amount of the hot cream into the egg yolk mixture, whisking constantly. Add a little more at a time until about one-third of the cream has been incorporated.
Pour the tempered egg mixture back into the saucepan with the remaining cream. Cook over low heat, stirring constantly with a wooden spoon, until the custard thickens enough to coat the back of the spoon and reaches 170-175 degrees F. Do not let it boil.
Pour the custard through a fine-mesh strainer into a clean container. Let rest at room temperature for 30 minutes, then stir in the vanilla extract.
Refrigerate, loosely covered, until completely cold and below 40 degrees F — at least 4 hours or overnight.
Pour the cold custard into your ice cream maker and churn according to the manufacturer directions, approximately 25-35 minutes.
Serve immediately as soft serve, or transfer to a freezer-safe container and freeze for 3-4 hours until firm.
