Cornstarch & milk mixture & vodka

Spoon - you're right, ingredient list and directions don't match.
But there is a whole method of using starch to make ice cream. See recipe (and related article) here for Sicilian Ice Cream.
If you want an Earl Grey flavored ice cream, I would use another recipe, for example at epicurious or martha stewart sites.
Last, the vodka reduces ice crystal formation and makes a smoother final dish,
Nancy