01 - Season chicken pieces thoroughly with salt and pepper. Toss with 2 tablespoons cornstarch until evenly coated on all sides.
02 - Heat 1 tablespoon 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 brown and cooked through. Remove and repeat with remaining oil and chicken. Set cooked chicken aside.
03 - In the same skillet, add minced garlic and grated ginger. Sauté for 30 seconds until fragrant, stirring constantly to prevent burning.
04 - Add pineapple juice, soy sauce, brown sugar, rice vinegar, and ketchup to the skillet. Stir thoroughly to combine and bring mixture to a gentle simmer.
05 - Stir in diced red bell pepper and pineapple chunks. Let mixture simmer for 3-4 minutes until vegetables begin to soften.
06 - Return cooked chicken to the pan. Mix cornstarch slurry thoroughly and stir into sauce. Cook while stirring constantly until sauce thickens and coats chicken evenly, approximately 2-3 minutes.
07 - Remove from heat immediately. Top with sliced green onions and sesame seeds before serving hot.