In a large oven safe skillet, whisk 1 cup water, soy sauce, sherry, sugar, molasses, and vinegar. Place the chicken skin side down in the skillet and arrange the ginger and garlic in between each.
Bring the mixture to a simmer over medium heat and cook for 5 minutes. Transfer the skillet to the oven and cook, uncovered, for 30 minutes longer.
Flip the chicken and continue to cook for 20 to 30 minutes longer, until internal temp reaches 195 degrees F. Carefully transfer the chicken to a platter and strain the cooking liquid rest for 5 minutes. Strain into a bowl and skim fat from the top and discard.
Set the oven to broil. Whisk the cornstarch and remaining ½ cup water into a small bowl. Heat 1 cup of the reserved soy mixture in the empty skillet over medium heat. Whisk in the cornstarch mixture and cook until thickened, about 1 minute. Return liquid to bowl and set aside.
place the chicken back into the empty skillet and broil about 4 minutes, until well browned.
Remove from oven and let rest before serving with additional sauce over rice.