01 - Season chicken pieces thoroughly with salt and black pepper. Toss coated chicken with 2 tablespoons cornstarch until each piece is evenly covered.
02 - Heat 1 tablespoon vegetable oil in a large skillet or wok over medium-high heat. Add half the chicken pieces and cook for 3 to 4 minutes per side until golden brown and cooked through. Remove cooked chicken and repeat with remaining oil and chicken. Set all chicken aside.
03 - In the same skillet, add minced garlic and grated ginger. Sauté for 30 seconds until fragrant, being careful not to burn.
04 - Pour in pineapple juice, soy sauce, brown sugar, rice vinegar, and ketchup. Stir continuously to combine and dissolve sugar. Bring mixture to a gentle simmer.
05 - Stir diced red bell pepper and pineapple chunks into the simmering sauce. Continue cooking for 3 to 4 minutes until vegetables begin to soften.
06 - Return cooked chicken to the pan. Whisk the cornstarch slurry again and stir into the sauce. Cook for 2 to 3 minutes while stirring constantly until sauce thickens and coats the chicken evenly.
07 - Remove from heat immediately. Garnish with sliced green onions and sesame seeds. Serve while hot over steamed jasmine rice.