01 - Season chicken pieces thoroughly with salt and pepper. Toss with 2 tablespoons cornstarch in a bowl 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 to 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 - Pour in pineapple juice, soy sauce, brown sugar, rice vinegar, and ketchup. Stir well to combine and dissolve sugar. Bring mixture to a gentle simmer.
05 - Stir in diced red bell pepper and pineapple chunks. Let simmer for 3 to 4 minutes until peppers begin to soften and pineapple is heated through.
06 - Return cooked chicken to the pan. Whisk cornstarch slurry again and stir into sauce. Cook for 2 to 3 minutes, stirring constantly, until sauce thickens and coats chicken evenly.
07 - Remove from heat immediately. Sprinkle sliced green onions and sesame seeds over the top. Serve hot over steamed jasmine rice or with stir-fried vegetables.