Prep the chicken. Pat the chicken dry and cut it into even, bite-size pieces.
Dry chicken browns better and helps the sauce cling.
Make the sauce. In a bowl, whisk together gochujang, soy sauce, honey, rice vinegar, sesame oil, and water. Add minced garlic, ginger, and gochugaru if using. Taste and adjust sweetness or heat.
Optional marinade. For deeper flavor, toss the chicken with half the sauce and let it sit for 15–30 minutes.
Keep the rest of the sauce for cooking and glazing.
Heat the pan. Set a large skillet over medium-high heat and add the neutral oil. When it shimmers, add the chicken in a single layer.
Sear until lightly browned. Cook the chicken for 3–4 minutes without moving too much, then stir and cook another 3–4 minutes until mostly cooked through.
Add the sauce. Pour in the remaining sauce. Lower heat to medium and let it bubble, stirring often.
If you want it extra glossy, mix cornstarch with 1 tablespoon water and stir in.
Reduce to a glaze. Let the sauce thicken until it coats the chicken and turns sticky, about 2–4 minutes. If it gets too thick, add a splash of water.
Finish and garnish. Turn off the heat. Sprinkle with green onions and sesame seeds.
Serve. Spoon over hot rice and add crisp veggies on the side.
The cool, fresh crunch balances the heat.