Combine in a plastic bag: sake, soy sauce, oil, ginger, garlic, and half the scallions. Add the chicken, cover, and refrigerate for at least 2 hours.
Preheat oven to 375°.
Spray a half baking pan with nonstick spray.
Place panko bread crumbs in a large bowl, season with salt and pepper, and stir well to combine.
Take chicken pieces from bag and roll and press them in the seasoned panko. Place the breaded chicken on the baking pan dish in a single layer.
Bake for 30 minutes, turn the pieces over, and bake for 30 minute more or until cooked through.
While chicken is baking, make the sauce:
Whisk hoisin, chili sauce, vinegar, and 2 tablespoons soy sauce together. Place chicken in a single layer on a platter or on individual plates and drizzle with sauce and scatter over the crushed peanuts and remaining scallions.