In a medium saucepan, bring milk, cinnamon stick, orange peel, vanilla bean and reserved seeds, peppercorns, cloves, cardamom, and star anise to a boil over medium heat. Remove from heat; cover and let steep for 20 minutes.

Strain milk, discarding solids. Return milk to pan. Whisk in brown sugar, egg yolks, flour, and kosher salt. Cook, whisking constantly, until thickened. Remove from heat; keep warm.

Meanwhile, in a small nonstick skillet, cook granulated sugar over medium heat, stirring occasionally, until deep amber colored. Whisking constantly, add caramel to milk mixture in a slow, steady stream until combined.

Strain mixture through a fine-mesh sieve into prepared Gingersnap Crumb Crust. Smooth top, and let cool for 10 minutes. Cover with a piece of plastic wrap, pressing wrap directly onto surface of filling. Refrigerate until set, at least 3 hours or up to 2 days.

Top with Salty Honey Meringue. Using a kitchen torch, carefully brown meringue. Garnish with sea salt, if desired.