Chicken Thighs, Grilled, Japanese, with Ginger-Soy Tare

Ingredients

• 1/2 cup mirin
• 1/2 cup sake
• 1 inch ginger root peeled and thinly sliced
• 2 medium garlic cloves peeled and smashed
• 6 shitake mushrooms
• 1/4 cup brown sugar packed
• 1/2 cup soy sauce
• 3 pounds chicken thighs trimmed and patted dry
• kosher salt and ground black pepper
• 1 lemon cut into 6 wedges
• 4 scallions thinly sliced