In a small bowl, add the honey, water, soy sauce, rice vinegar, garlic, ginger, and ½ teaspoon of cornstarch. Whisk together and set aside.
In a medium bowl, add the remaining ¼ cup cornstarch and the egg. Whisk together until well combined and set aside.
Heat the oil in a large skillet over medium heat until it shimmers. Meanwhile, season the chicken generously with salt and pepper and transfer the breasts to the cornstarch and egg mixture. Flip and rearrange the chicken until all pieces are coated in batter.
Let any excess drip off and place the chicken into the hot pan. Cook, undisturbed, until golden, about 5 minutes. Flip and cook on the other side until the chicken is golden brown and cooked through to 165°F, another 4 to 5 minutes.
Remove the chicken to a plate and pour the sauce into the pan. Bring to a boil over high heat, then reduce to medium and simmer until thickened, stirring occasionally, about 4 minutes.
Return the chicken to the pan and coat with the sauce. Serve the chicken on top of steamed rice, if using, and drizzle more sauce over the top. Garnish with green onions and serve immediately.
