Grate the garlic and ginger directly into a large bowl. Add the soy sauce, mirin, vinegar, and sesame oil. Whisk together, then add the chicken to the sauce. Let marinate for as long as you have - 2 - 4 hours is ideal.
When ready to cook, transfer the chicken, skin side up, and all the juices from the marinade to a baking dish. Preheat the oven to 400F. Bake uncovered for 30 - 40 minutes until cooked through.
Serve with scallions, extra juices from the pan, and rice, or as desired.