To ward off fears about bacteria, always refrigerate any dish while it is marinating.
1½ pounds chicken thighs, bone in
2 tablespoons hoisin sauce
1 tablespoon dark soy sauce
4 tablespoons water
1 teaspoon sugar
⅛ teaspoon white pepper, or to taste
1 large garlic clove, chopped
Wash the chicken thighs and pat dry. Remove the skin and make 2 diagonal cuts on each side of the thigh.
Mix together the hoisin sauce, dark soy sauce, water, sugar, white pepper, and garlic. Place the sauce in a large, zipper-lock plastic bag. Add the chicken, shaking the bag slightly to make sure the sauce coats all the chicken. Seal the bag and place in the refrigerator. Marinate the chicken for 2–3 hours, turning the bag occasionally.
Preheat the oven to 400°F.
Remove the chicken thighs from the bag, reserving the sauce. Place the thighs on a baking sheet sprayed with cooking spray. Brush on half of the sauce, making sure both sides of the thighs are covered. Bake the thighs for 15 minutes. Brush on the remainder of the sauce, and bake for another 15 minutes, or until the thighs are cooked.