Prep the chicken. Pat the chicken dry. Season with salt, pepper, and a pinch of garlic powder. This helps the flavor soak into the meat.

Set up the coating station. In one bowl, whisk the eggs. In a second bowl, mix cornstarch and flour with a pinch of salt and pepper.

Coat the chicken. Dip each piece in egg, then into the cornstarch-flour mixture. Shake off extra coating so you don’t end up with clumps in the pan.

Heat the oil. Add about 1/2 inch of oil to a deep skillet or wok. Heat over medium-high until it shimmers. A small pinch of coating should sizzle on contact.

Fry the chicken in batches. Cook pieces for 3–4 minutes per side until golden and cooked through. Do not crowd the pan. Transfer to a wire rack or paper towels. Crisp tip: Keep the heat steady; too low makes the coating soggy.

Stir-fry the vegetables. Pour off most of the oil, leaving 1 tablespoon in the pan. Add chopped peppers and onions. Cook 2–3 minutes until slightly tender but still crisp.

Add pineapple. Toss in pineapple chunks and stir for 30 seconds. You want them warmed and lightly caramelized in spots.

Make the sauce. In a small bowl, whisk ketchup, vinegar, sugar, soy sauce, oyster sauce (if using), and pineapple juice. Bring the mixture to a simmer in the pan with the vegetables.

Thicken the sauce. Stir the cornstarch slurry, then pour it into the simmering sauce. Stir constantly until glossy and thick, about 1–2 minutes. If too thick, add a splash of water. If too thin, simmer another minute.

Combine everything. Add the fried chicken back to the pan. Toss gently so every piece is coated and warmed through, about 1 minute.

Finish and serve. Taste and adjust: add a pinch of sugar for sweetness, more vinegar for tang, or a splash of soy for salt. Garnish with sesame seeds and green onions. Serve hot over rice.