Cut the chicken into 1-inch pieces. In a mixing bowl, combine the chicken with salt, pepper, garlic powder, coconut aminos, mirin, egg whites, and cornstarch. Toss to coat evenly, then let marinate for at least 30 minutes or up to 3 hours.
In a large skillet, heat enough oil over medium-high heat to coat the bottom of the pan. Once hot, add the chicken pieces in a single layer—being careful not to overcrowd the pan. Cook in batches if needed. Sear the chicken for 3–4 minutes per side, until golden brown and cooked through. Transfer to a wire rack or a paper towel-lined plate to drain. Discard the used oil and wipe the skillet clean.
To the skillet, add the oil, ginger and garlic, and sauté for 2 minutes until fragrant. Pour in the sauce mixture (reserving the cornstarch slurry) and bring to a simmer. Stir in the cornstarch slurry, cooking and stirring continuously until the sauce thickens. Return the chicken to the skillet and toss to coat. Let it simmer for 1–2 more minutes until the chicken is fully coated and heated through.
Serve the orange chicken over a bed of white rice alongside your favorite stir-fried vegetables. Enjoy!