In a shallow bowl, combine the flour, 1/2 cup cornstarch, salt, and black pepper. Place the beaten eggs in a second bowl.

Dip the chicken pieces into the egg, allowing the excess to drip off, then toss them in the flour mixture until lightly coated.

Heat the vegetable oil in a large skillet over medium to medium-high heat. Cook the chicken in batches for about 3–4 minutes per side, or until golden brown and cooked through. Do not overcrowd the skillet. Transfer the cooked chicken to a paper-towel-lined plate. Chicken should reach an internal temperature of 165°F.

Carefully remove excess oil from the skillet, leaving about 1 tbsp behind. Add the red bell pepper and cook for 2–3 minutes, until slightly softened.

Add the pineapple juice, chicken broth, brown sugar, rice vinegar, ketchup, and soy sauce. Stir well and bring the mixture to a gentle simmer.

In a small bowl, whisk together 1 tbsp cornstarch and 2 tbsp cold water until smooth. Slowly stir the slurry into the simmering sauce. Cook for 1–2 minutes, stirring, until the sauce becomes glossy and thick enough to coat a spoon.

Add the pineapple chunks and cooked chicken to the skillet. Toss gently until everything is evenly coated and heated through, about 1–2 minutes.

Remove from the heat and serve immediately over cooked rice. Garnish with sliced green onions if desired.