Custard Ice Cream Base

Method

1. Warm the heavy cream, whole milk, 1/2 cup of the granulated sugar, and the kosher salt in a heavy saucepan over medium heat, stirring, until the sugar dissolves and steam rises but the mixture never simmers.
2. Whisk the egg yolks with the remaining 1/4 cup granulated sugar in a bowl until pale and slightly thickened, about 1 minute.
3. Ladle about a cup of the hot dairy into the yolks in a thin stream while whisking constantly, then pour that mixture back into the saucepan. Adding it all at once scrambles the yolks.
4. Cook over medium-low heat, stirring constantly with a spatula and scraping the corners of the pan, until the custard thickens enough to coat the back of the spatula and holds a clean line when you draw a finger through it, 170 to 175 degrees F (79 degrees C) on an instant-read thermometer. Holding it at that temperature also pasteurizes the yolks; do not let it boil or it will curdle.
5. Strain the custard through a fine sieve into a clean bowl, stir in the vanilla extract, and set the bowl in an ice bath, stirring until cool.
6. Cover and refrigerate at least 6 hours or overnight, then churn in an ice cream maker according to the manufacturer's directions and freeze 4 hours for a firm scoop.