In a medium bowl, whisk together miso paste, sesame oil, olive oil, mirin, soy sauce, salt and pepper. Place the chicken thighs and legs in a ziplock bag. Add the prepared sauce and evenly distribute it all over the chicken. Squeeze out the air, zip and marinade for 20-30 minutes.
Preheat the oven to 350°F. Line the baking pan with an aluminum foil.
Remove the chicken from the bag and place them in the prepared pan. Bake for 35 minutes, or until the internal temperature reaches 170°F.