▢¾-1 cup canola oil for frying ▢½ cup cornstarch ▢3-4 chicken breasts or chicken thighs, cut into 1-inch pieces ▢2 eggs beaten ▢½ cup all-purpose flour plus more if needed ▢1 red bell pepper cut into 1-inch chunks ▢1 green bell pepper cut into 1-inch chunks ▢1 cup pineapple chunks Sweet and Sour Sauce ▢¾ cup water ▢⅓ cup pineapple juice ▢⅓ cup vinegar ▢⅓ cup soy sauce ▢⅓ cup ketchup ▢½ cup sugar ▢¼ cup packed brown sugar ▢⅛ teaspoon salt ▢3 tablespoons cornstarch mixed with ¼ cup water
Prepare the sauce: In a medium pot combine water, pineapple juice, vinegar, soy sauce, ketchup, both sugars, and salt over low heat. Cook, stirring occasionally, while frying chicken.
For the chicken, heat 1–1½ inches of oil in a large frying pan over medium-high heat.
Place cornstarch in a large resealable plastic bag, then add chicken pieces. Shake until all the pieces are evenly coated. Beat eggs in a small bowl. Place flour in a separate bowl. Dip each piece of chicken into egg, then into flour. Once coated, add to the hot oil.
Cook chicken for 2–3 minutes, flipping with metal tongs, until cooked through and crispy. Once crisp, place chicken on a paper towel–lined plate. Once all the pieces have been cooked, discard all but a few tablespoons of oil.
Add bell peppers and pineapple to the frying pan and cook for 1–2 minutes, or until peppers are crisp-tender. Meanwhile, finish the sauce by adding cornstarch-water slurry. Mix and bring to a low boil, then cook, stirring, for about 2 minutes, until thickened.
Add the sauce to the pineapple and peppers. Add the chicken and stir to coat. Cook until sauce is bubbling, 4–5 minutes more.