In a large plastic resealable bag, add the soy sauce, brown sugar, garlic, and grated ginger and mix until the sugar is dissolved. Put the chicken thighs into the bag with the marinade. Seal and refrigerate overnight.
Preheat pan over medium heat.
Remove the chicken from the marinade and set aside. Put the marinade in a pot over medium heat and reduce by half. Spray pan with nonstick cooking spray, arrange the chicken in pan, skin-side down cover pan and cook for 7 minutes per side. Brush the chicken liberally with the reduced marinade before removing from pan.
Place chicken back in pan with the rest of the reduced marinade and 1/4 cup water. Steam over medium heat for 10 minutes.
Place ginger rice on plate top with 1 chicken thigh and sprinkle with scallions.