Marinate the chicken by mixing gochujang, honey, soy sauce, sesame oil, garlic, ginger, salt, and pepper in a bowl. Add chicken pieces and coat well. Marinate for at least 10 minutes, preferably 2 hours.

Heat vegetable oil in a skillet over medium-high heat until shimmering.

Sauté chopped onion and bell pepper for about 3-4 minutes until softened.

Add the marinated chicken to the skillet and cook for 5-7 minutes until fully cooked and golden brown.

Return the sautéed vegetables to the skillet, stir to combine, and warm for another 2-3 minutes.

Simmer for a couple of minutes until the sauce thickens, stirring occasionally.

Garnish with sliced green onions and sesame seeds before serving.