For ice cream, heat 1 cup cream and milk with the scraped seeds of vanilla beans (let pods steep in cream for extra flavour). Keep just below a simmer.
In a bowl over a pot of gently simmering water, whisk vigorously egg yolks, sugar, salt and cinnamon until thick and a pale buttery colour, about 3 minutes.
Remove from heat. Slowly ladle heated cream mixture into eggs, whisk constantly until all cream has been added (discard vanilla beans).
Return mixture to medium heat and stir with a wooden spoon until it coats the spoon, about 3 minutes. Strain and chill mixture completely.
Whip remaining 1 cup cream to soft peaks and fold into chilled custard. Freeze in an ice cream maker following manufacturer’s instructions, then scrape into a container and freeze until firm, about 2 hours.