Mix all the sauce ingredients in a small bowl and set it aside.
Combine the chicken pieces, vegetable oil, and salt in a big bowl. Mix well and let it marinate for 10 to 20 minutes.
Add the beaten egg into the bowl with the chicken. Stir to mix well. Add the cornstarch. Stir to coat the chicken until it forms an uneven coating with a little dry cornstarch left unattached.
Heat the stir-fry oil in a heavy-duty skillet until hot, until it just starts to smoke. Add the chicken all at once and spread it out into a single layer in the skillet. Separate the chicken pieces with a pair of tongs or chopsticks.
Cook without touching the chicken for 2 to 3 minutes, or until the bottom turns golden. Flip to brown the other side, 2 to 3 minutes. Transfer the chicken to a big plate and remove the pan from the stove. Let cool for 2 to 3 minutes.
Place the pan back onto the stove and turn to medium heat. You should still have 1 to 2 tablespoons of oil in the pan. Add the dried chili pepper, garlic, and ginger. Cook and stir a few times until it releases its fragrance.
Stir the sauce again to dissolve the cornstarch completely. Pour it into the pan. Stir and cook until it thickens, when you can draw a line on the bottom with a spatula without the sauce running back immediately.
Add back the chicken pieces. Stir to coat the chicken with sauce, 30 seconds. Transfer everything to a plate immediately.
Serve hot as main over steamed rice with blanched broccoli.