Put 2 cups heavy cream, 1 cup milk, 1/2 cup Grade B maple syrup and a pinch of salt in a sauce pan. Add either 1–1/2 tsp vanilla extract or 1 whole vanilla bean, split lengthwise and seeds scraped into mixture. Include the pod in the mixture, too. Heat until steaming, but do not let boil.
In a bowl, combine 4–1/2 TBL (that’s a generous 1/4 cup) of corn starch and 3/4 cup milk. Stir with fingertips to confirm there are no lumps. Remove vanilla pod from pot. Add cornstarch mixture, cook, stirring until it reaches a boil. Reduce heat to low and let cook for 5 minutes or until thick, stirring so it won’t scorch.
Strain and chill a couple of hours and freeze in ice cream maker.