2In a bowl, combine the chicken with the egg white, 1/2 teaspoon kosher salt, and cornstarch. Stir to coat the chicken evenly. Let sit for 15 minutes at room temperature or up to overnight in the refrigerator.
3Make the sweet and sour sauce:
4Whisk together the pineapple juice, vinegar, ketchup, 1/2 teaspoon kosher salt, and brown sugar.
5Stir-fry the chicken over high heat:
6Heat a large frying pan or wok over high heat until a bead of water instantly sizzles and evaporates. Pour in 1 tablespoon of cooking oil and swirl to coat. It's important that the pan is very hot.
7Add the chicken and spread the pieces out in one layer. Let the chicken fry untouched for 1 minute, until the bottoms are browned.
8Flip and fry the other side for 1 minute. The chicken should still be pinkish in the middle. Dish out the chicken onto a clean plate, leaving as much oil in the pan as possible.
9Stir-fry the bell pepper and ginger:
10Reduce the heat to medium and add the remaining 1 teaspoon of cooking oil. Let the oil heat up before adding the bell pepper chunks and ginger. Fry for 1 minute.
11Add the pineapple, sauce, and then, the chicken:
12Add the pineapple chunks and the sweet and sour sauce. Turn up the heat to high. When the sauce is simmering, add the chicken pieces back in.
13Let simmer for 1 to 2 minutes, until the chicken is cooked through. Timing depends on how thick you've cut your chicken. The best way to tell if the chicken is done is to take a piece out and cut into it. If it's pink, add another minute to the cooking.
14Adjust the seasoning and serve:
15Taste the sauce and add more brown sugar or vinegar to suit your tastes, if you’d like.
