In a large bowl, combine chicken, soy sauce, sugar, vinegar, garlic, bay leaves, and pepper. Mix well. Then cover with saran wrap and let marinate for 1-2 hours.
In a caldero or a pan with high sides, place oil and allow to heat up.
Remove the chicken from the marinade. Set the marinade aside.
Add and fry chicken in batches as necessary to develop color on all sides of the chicken. Set them aside when done.
Add more oil and sautee white onion and the white parts of the scallion (reserve the green part for the topping at the end)
Then add the water and the remaining marinade. Add the chicken back in. Cook for about 15 minutes covered.
Flip the chicken and let cook for ten more minutes covered.
Prepare cornstarch slurry by mixing 1 tbs of cornstarch and 1/2 tbs water and mix.
Remove the chicken (check that the internal temp is at 165) and set aside.
To the remaining liquid in pot, add the slurry. (You can add more slurry as desired to get to desired thickness)
Once you get to the desired thickness, pour the sauce over the chicken and top with the cut scallions.