Add half and half to a medium saucepan, sprinkle the gelatin over the top and let sit for 5 minutes. The surface will wrinkle as the bloom develops. If using vanilla bean, add now as well.
Set the saucepan over low heat and warm, whisking occasionally, for about two minutes until the gelatin dissolves completely. The milk should not be simmering or even steaming yet.
Add the sugar and continue to warm the milk until sugar dissolves - again, do not let it come to a simmer.
Remove from the heat, whisk in the vanilla extract, salt, and turmeric.
Pour into serving dishes and chill for at least 3 hours, though overnight is best.