Trim any excess fat from the chicken and pat pieces dry with paper towels; season both sides lightly with kosher salt and black pepper.

Heat 1 tablespoon of oil in a 12-inch oven-safe skillet over medium-high heat until shimmering, then add chicken in a single layer without crowding and sear 2 to 3 minutes per side until deep golden; work in batches if needed and add the remaining tablespoon oil between batches.

Preheat the oven to 400°F while searing; return all seared pieces to the skillet (or transfer to a 9×13-inch baking dish) and bake 8 to 12 minutes depending on thickness until an instant-read thermometer reads 160–162°F (carryover will bring it to 165°F). Remove and let rest while you make the sauce.

Wipe excess burnt bits from the skillet, set over medium heat, add 1 tablespoon butter and sauté the minced garlic for about 30 seconds until fragrant (do not brown). Stir in the honey, soy sauce, rice vinegar, grated ginger, and red pepper flakes and bring to a gentle simmer.

Whisk 1 tablespoon cornstarch with 1 tablespoon cold water to make a slurry; remove the skillet from the highest heat and stir the slurry into the sauce, then return to low heat and stir until the sauce thickens and becomes glossy, about 30–60 seconds. Turn off the heat and stir in 1 tablespoon butter.

Return the chicken to the skillet and spoon the sauce over each piece, letting them sit in the warm sauce for 1–2 minutes so it clings. Garnish with sliced green onions and toasted sesame seeds if desired and serve hot.