Steps
- Freeze the ice cream maker bowl for at least 12 hours, following its instructions. Heat 300ml of whole buttermilk, 360ml of heavy cream, 175g of sugar, and 1 pinch of salt over medium-low heat until steaming.
- Whisk 2 large egg yolks, 1 large egg, and 1 tablespoon of vanilla bean paste with the grated zest of 1 large lemon.
- Slowly whisk half the warm cream mixture into the eggs, then return everything to the saucepan. Stir over low heat until the custard coats a spoon and reaches 170°F / 77°C.
- Strain into a bowl, cover the surface, and refrigerate until completely cold. Churn for 25-30 minutes, or according to the machine instructions, until thick and softly frozen.
- Layer into a freezer-safe container with 70g of crushed vanilla cookies, swirling gently to distribute. Cover and freeze for at least 2 hours, until firm enough to scoop.