This is 3 minutes of work, 30 minutes in your ice cream maker, and then (at least) an hour in the freezer.
500 ml. heavy cream (or dairy-free/Pareve substitute)
300 ml. (1¼ cups) milk (or dairy-free/Pareve substitute such as soy milk/rice milk/almond milk)
6-8 Tbsp. sugar (if using dairy-free cream substitute, reduce to 4 Tbsp., as it is significantly sweeter)
1 vanilla bean, scraped for seeds
1 tsp. pistachio paste
Whisk all ingredients together in a bowl.
Churn in an ice-cream maker for 25-30 minutes (if you do not have an ice cream maker, place in a closed container in the freezer – remove and mix every ½ an hour until it reaches desired consistency).
pour into freezer-friendly lidded-container, and freeze.