• Gather all the ingredients.
  

To Marinate

• Combine 1 cup shio koji and 1 Tbsp soy sauce in a bowl or measuring cup.
  
• Season both sides of 8 pieces boneless, skin-on chicken thighs with freshly ground black pepper.
  
• Pour the shio koji mixture on the chicken pieces and coat them well on both sides. Cover and let it marinate in the refrigerator for 30 minutes (minimum) or up to 3 hours.
  

To Bake

• Preheat the oven to 350ºF (180ºC). For a convection oven, reduce cooking temperature by 25ºF (15ºC). Remove the shio koji as much as possible and transfer to a baking sheet lined with parchment paper.
  
• If your oven doesn‘t come with a temperature probe, you can use a ThermoWorks Chef Alarm. Insert the stem of the probe into the thickest part of the chicken, or in the center of the chicken if it is even in thickness.
  
• Bake at 350ºF (180ºC) until the internal temperature of the chicken reaches to 165ºF (74ºC), roughly 25 minutes.
  
• Once the chicken is cooked through, change the oven setting from Bake to Broil. Broil the chicken until the skin has nice char, about 3–5 minutes (depends on how far the chicken is from the heat source). Remove from the oven.
  
• Cut each chicken thigh into 4 pieces (if you eat with chopsticks) and serve immediately.
  

To Store

• You can keep the leftovers in an airtight container and store in the refrigerator for up to 4 days and in the freezer for 2–3 months.