Rinse the chicken legs and pat dry with paper towels. In a shallow dish or plastic bag, combine the sake, 1/4 cup soy sauce, oil, ginger, garlic, and half the scallions. Add the chicken legs, cover, and refrigerate for at least 2 hours.
Preheat oven to 350 degrees F.
Lightly grease a baking sheet with peanut oil. Place panko bread crumbs in a large plastic or paper bag, season with salt and pepper, and shake well to combine. Take 2 or 3 chicken legs at a time from the marinade and shake them in the seasoned bread crumbs until well coated. Place the breaded chicken legs on a baking sheet. Bake for 15 minutes, turn the pieces over, and bake for 15 minutes more or until cooked through. Remove chicken to a wire rack to cool.
Make the sauce by whisking hoisin, chili sauce, vinegar, and remaining 1 teaspoon soy sauce together. Place chicken legs in a single layer on a platter, drizzle with sauce and scatter over the crushed peanuts and remaining scallions. Serve warm or at room temperature.