4-inch piece fresh ginger, peeled and chopped
2 cups low-fat buttermilk
1 cup whole milk
4 large egg yolks
3/4 cup granulated sugar
In a large liquid measuring cup or a small bowl, combine the ginger and buttermilk. Refrigerate for at least 1 hour, and up to 3 hours.
Heat the milk in a medium saucepan over medium heat until hot but not boiling. Meanwhile, in a medium bowl, whisk the yolks and sugar together until combined. Whisking constantly, gradually add the hot milk to the egg yolks. Pour the mixture back into the saucepan, return it to medium-low heat, and stir constantly with a wooden spoon until it is thickened and coats the back of the spoon, 6 to 8 minutes. Remove from the heat.
Strain the buttermilk through a fine-mesh strainer into the milk mixture and whisk well to combine; discard the ginger. Strain the mixture into a medium bowl. Set the bowl in a slightly larger bowl filled with ice water and stir occasionally until the ice cream base is cold.
Freeze the ice cream in an ice-cream maker following the manufacturer's instructions. Transfer to an airtight container and freeze for up to 1 month.
Make about 1 quart.
— Adapted from "Try this at Home" by Richard Blais