1. Combine soy sauce, pepper, garlic powder, and ginger to make a marinade. Add chicken thighs and marinade to a zip-top bag then refrigerate 1-6 hours.
2. Remove chicken from marinade onto a few layers of paper towels, keeping marinade to be used later.
3. Add enough oil to a large skillet to generously coat the bottom then heat over medium-high heat until oil is shimmering. Place all chicken thighs into skillet then cook 5-7 minutes on each side or until nicely browned. Remove chicken from skillet.
4. Add onions to hot skillet with pan drippings then sauté for 3 minutes. Add garlic then cook an additional 2 minutes.
5. Add reserved marinade to onions to deglaze the pan then cook 5 minutes or until marinade is reduced by half.
6. Add chicken broth and rice then bring to a boil. Once boiling, reduce heat to medium-low, cover then cook for 10 minutes. Stir with a fork, taking care to scrape the bottom of the pan to ensure the rice isn’t sticking.
7. Arrange chicken in skillet over rice, cover then continue cooking 10-15 minutes over low heat until rice is done.
8. To serve, drizzle Yum Yum sauce over chicken then garnish with chopped chives or scallions if desired.