1 - Coat the chicken with egg white: In a bowl, combine the chicken with the egg white, 1/2 teaspoon kosher salt, and cornstarch.

2 - Stir to coat the chicken evenly.

3 - Let sit for 15 minutes at room temperature or up to overnight in the refrigerator.

4 - Make the sweet and sour sauce: Whisk together the pineapple juice, vinegar, ketchup, 1/2 teaspoon kosher salt, and brown sugar.

5 - Stir-fry the chicken over high heat: Heat a large frying pan or wok over high heat until a bead of water instantly sizzles and evaporates.