01 - Season chicken pieces with salt and pepper in a bowl. Toss with 2 tbsp cornstarch until evenly coated.
02 - Heat 1 tbsp vegetable oil in a large skillet or wok over medium-high heat. Add half the chicken and cook for 3–4 minutes per side until golden and cooked through. Remove and repeat with remaining oil and chicken. Set aside.
03 - Add garlic and ginger to the same skillet. Sauté for 30 seconds until fragrant.
04 - Add pineapple juice, soy sauce, brown sugar, rice vinegar, and ketchup. Stir to combine and bring to a simmer.
05 - Stir in diced red bell pepper and pineapple chunks. Simmer for 3–4 minutes.
06 - Return chicken to the pan. Mix cornstarch slurry and stir into sauce. Cook stirring until sauce thickens and chicken is well coated for 2–3 minutes.
07 - Remove from heat. Top with sliced green onions and sesame seeds before serving.