In a medium bowl, toss the sliced chicken thighs with cornstarch until evenly coated. This will help create a nice texture when cooked.
Heat vegetable oil in a large skillet or wok over medium-high heat.
Once the oil is hot, add the chicken to the skillet in a single layer. Cook for about 5-7 minutes, stirring occasionally, until the chicken is browned and cooked through. Remove from the skillet and set aside.
In the same skillet, add the sliced bell peppers and onion. Sauté for about 3-4 minutes, or until the vegetables are tender but still crisp.
Add the minced garlic and ginger to the skillet and cook for an additional 1 minute until fragrant.
Return the cooked chicken to the skillet, and stir in the gochujang, soy sauce, honey, and sesame oil. Mix well to coat everything in the sauce. Cook for an additional 2-3 minutes, allowing the sauce to thicken slightly.
Remove from heat and transfer to a serving dish. Garnish with sesame seeds and chopped green onions.