1. Heat a small saucepan over low heat; add butter and vanilla beans. Cook over low heat until butter takes on vanilla aroma (about 15-20 minutes). Strain butter; keep warm.
2. In a small bowl, combine sugars and cinnamon; set aside. In a large bowl, toss popcorn while drizzling with 1/4 cup vanilla butter (reserve remaining vanilla butter to use on toast or muffins). Sprinkle popcorn with dry mixture; toss. Sprinkle with sea salt.