Pat the chicken dry and toss with 1 tablespoon soy sauce, 1 teaspoon ginger, and the black pepper. Let it sit 10 minutes while you make the sauce.
Whisk the gochujang, honey, 1 tablespoon soy sauce, rice vinegar, brown sugar, garlic, 1 teaspoon ginger, sesame oil, and water in a bowl. Set aside.
Add the cornstarch to the chicken and toss until every piece is lightly and evenly coated. Shake off the excess in a colander so there are no dry clumps.
Arrange the chicken in a single layer in the air fryer basket, pieces not touching. Spray the tops generously with oil. Air fry at 400F (200C) for 12 minutes, flipping and spraying again halfway.
For extra crunch, air fry a second time at 400F for 3 to 4 minutes until deep golden and crisp. Work in batches if your basket is small.
Pour the sauce into a large wide pan over medium heat. Simmer 1 to 2 minutes until it thickens and coats the back of a spoon.
Turn the heat to low or off, add the hot chicken, and toss quickly for about 30 seconds until glazed. Do not let it boil in the sauce or the coating softens.
Tip onto a plate, scatter with sesame seeds and scallions, and serve right away.