Pre heat the oven to 450˚ F with the rack in the middle.
Line a baking sheet with tin foil.
Make a few slits on the top of the chicken, slicing though the skin to the bone.
In a large bowl whisk together the rice wine vinegar, miso, soy sauce, ginger, sugar and pepper.
Place the chicken into the sauce mixture and rub to coat on all sides, being sure to get the sauce into the slits.
Place the chicken skin side up on the baking sheet. with the sauce.
In the empty (do not rinse) bowl add the mushrooms and the whites of the scallions. Toss to coat with sauce residue.
Add this mixture to the sheet pan, scattering around the chicken.
Roast until the chicken and mushrooms are browned and the internal temperature of the thickest parts of the thighs and drumsticks reads 175˚F ~ about 30-40 minutes.
With tongs, transfer the chicken to a serving plate and sauce with the mushroom mixture and the pan drippings.
Top with the green parts of the scallions.
Serve with rice, conscous, quinoa or pasta.