Cut chicken into thin strips (1-2 inches), season with salt and pepper, and let sit for 10 minutes.

Cut onion, bell peppers, and pineapple into bite-sized pieces and set aside.

Prepare batter by mixing flour, cornstarch, water, and egg white until light and runny.

Coat chicken in cornstarch, remove excess, then dip into batter until fully coated.

Heat vegetable oil to 350°F (medium-high heat).

Deep fry chicken strips in batches for 5 minutes until golden brown and cooked through.

Place fried chicken on paper towel-lined dish or wire rack to drain excess oil and fan dry for crispiness.

In a small pan, combine sauce ingredients (excluding cornstarch and water mixture).

Bring sauce to a rapid boil until sugar dissolves.

Add cornstarch and water mixture to the sauce.

Reduce heat to low and stir until thickened.

Taste and adjust sauce seasoning as needed.

Add vegetables to the sauce and simmer for a few minutes.

Combine chicken and sauce before serving, or serve separately.