Dorie Greenspan’s Sheet-Pan Balsamic Chicken with Baby Potatoes and Mushrooms

Ingredients

• 1½ pounds small potatoes, scrubbed and halved if large
• ½ pound white mushrooms, wiped clean, trimmed and cut in half if large
• 1 large shallot or medium onion, cut into 8 wedges, rinsed and patted dry
• 4 garlic cloves, unpeeled
• 8 sprigs fresh rosemary, divided
• 8 sprigs fresh thyme, divided
• Fine sea salt and freshly ground black pepper
• 6 tablespoons extra-virgin olive oil, divided
• 4 tablespoons balsamic vinegar, divided
• 4 whole chicken legs (thigh and drumstick)