Preheat the oven to 425°F (220°C). Line a baking sheet with foil or parchment and set a wire rack on top. Lightly oil the rack (or brush with a little oil) to prevent sticking.
Pat the wings very dry with paper towels. For best results, let them rest uncovered at room temperature for 15 minutes while the oven heats.
In a large bowl, combine potato starch (or cornstarch), baking powder (if using), salt, and pepper. Toss the wings until evenly coated. Drizzle with vegetable oil and toss again to lightly coat.
Arrange wings in a single layer on the rack. Bake for 30 minutes, flip, then bake 25–30 minutes more until deeply golden and crisp. Check that the thickest part reaches 165°F (74°C).
While the wings bake, make the sauce: in a small saucepan over medium heat, whisk together gochujang, honey, soy sauce, rice vinegar, sesame oil, garlic, gochugaru, and ginger. Simmer 2–4 minutes, stirring, until glossy and slightly thickened.
Transfer hot wings to a clean mixing bowl. Pour over the warm sauce and toss until every wing is well coated.
Finish with toasted sesame seeds and sliced green onions. Serve immediately.