Substitute two teaspoons pure vanilla extract if you don't have a vanilla bean.
3 1/3 cups 2% reduced-fat milk
1 cup half-and-half
1 (6-inch) vanilla bean, split lengthwise
1 cup sugar
3 large egg yolks
How to Make It
Combine milk and half-and-half in a medium, heavy saucepan. Scrape seeds from vanilla bean; add seeds and bean to pan. Bring milk mixture to a boil. Remove from heat. Remove bean; discard.
Combine sugar and egg yolks; beat with mixer at high speed until thick and pale. Gradually add half of hot milk mixture to sugar mixture, stirring constantly with a whisk. Return milk mixture to pan. Cook over medium-low heat 2 minutes or until thermometer registers 160°; stir constantly.
Place pan in an ice-filled bowl. Cool, stirring occasionally. Pour mixture into the freezer can of an ice-cream freezer; freeze according to manufacturer's instructions. Spoon ice cream into a freezer-safe container; cover and freeze 1 hour or until firm.