In a medium bowl, whisk together the egg white and cornstarch until the mixture is smooth and slightly frothy, which should take about 30 seconds.
Add the chicken, sprinkle with a pinch of salt, and toss to coat it evenly. Set aside.
In a small bowl, combine the orange juice, ketchup, red wine vinegar, honey, soy sauce, and the remaining 2 teaspoons of cornstarch. Whisk until smooth and set aside.
Heat 1 1/2 tablespoons of oil in a 12-inch non-stick skillet over medium-high heat.
Add the chicken and cook for about 3 minutes, until golden brown on one side. Flip the chicken and cook for an additional 3 minutes, or until fully cooked through.
Transfer the chicken to a plate. In the same skillet, heat the remaining 1/2 tablespoon of oil over medium-high heat.
Add the bell pepper and sauté for 2-3 minutes, until crisp-tender. Stir in about 3/4 of the green onions, along with the ginger and garlic, and cook for another 30 seconds.
Pour the orange juice mixture into the skillet and cook, stirring constantly, until the sauce thickens, about 30-60 seconds. Add the chicken and pineapple, tossing to coat.
Serve warm, garnished with the remaining green onions.