In a bowl, whisk eggs and season with the salt and pepper. Add the chicken pieces and stir to coat in egg mixture.
In a different mixing bowl, add the cornstarch and flour and combine.
Coat the chicken with the cornstarch/flour mixture on all sides.
Heat the oil over medium-high to high heat.
Once the oil is hot, add chicken in batches and cook until all of the chicken is cooked. Transfer cooked chicken to a baking sheet.
In the same skillet, add the butter, bell peppers, pineapples and onion and cook until tender 3-4 minutes.
Add garlic and cook for another 30 seconds or until fragrant.
In a medium bowl, whisk the ingredients for the sauce: the sugar, brown sugar, vinegar, ketchup and soy sauce until combined.
Add the chicken to the vegetables, pour in the sauce and cook until it starts to bubble and thickens and the chicken is reheated.
Serve with sesame seeds or green onion to garnish, totally optional.