Mix the mirin, miso paste, ginger, sugar, garlic and soy sauce together. Coat the chicken with this paste and marinate for at least 2 hours or you can also marinate this overnight. Bring the chicken to room temperature.
Preheat oven to 190C/380F and line a baking tray with parchment. Place the chicken pieces on the tray and allow the excess paste to drip off. Roast the chicken for 20 minutes. Baste with the oil from the chicken and then roast for 10 minutes or until cooked through.
Meanwhile while the chicken is cooking, make the rice. Rinse the rice several times until the water runs clear. Then add the stock, ginger and garlic and bring to a boil. Reduce heat to low and keep the lid on and steam for 15 minutes. Add the sesame oil and stir. Serve the chicken with the rice.