Step 1: Coat the chicken with egg white:

Step 2: In 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.

Step 3: Make the sweet and sour sauce:

Step 4: Whisk together the pineapple juice, vinegar, ketchup, 1/2 teaspoon kosher salt, and brown sugar.

Step 5: Stir-fry the chicken over high heat:

Step 6: Heat 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.

Step 7: Add the chicken and spread the pieces out in one layer. Let the chicken fry untouched for 1 minute, until the bottoms are browned.

Step 8: Flip 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.

Step 9: Stir-fry the bell pepper and ginger:

Step 10: Reduce 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.

Step 11: Add the pineapple, sauce, and then, the chicken:

Step 12: Add 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.

Step 13: Let 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.

Step 14: Adjust the seasoning and serve:

Step 15: Taste the sauce and add more brown sugar or vinegar to suit your tastes, if you’d like.

Step 16: Serve hot with steamed white or brown rice.