Wild Mushroom Risotto

INGREDIENTS

• 9 1/2 tablespoons butter, divided
• 1 1/2 pounds fresh wild mushrooms
• (such as cèpe [porcini], hen of the woods, chanterelle, or stemmed shiitake); large mushrooms sliced, small mushrooms halved or quartered
• 7 cups (about) low-salt chicken broth
• 1 tablespoon extra-virgin olive oil
• 3/4 cup finely chopped leek (white and pale green parts only)
• 1 1/4 cups arborio rice (8 to 9 ounces)
• 1/4 cup dry white wine
• 1/4 cup dry white vermouth
• 1/4 cup grated Parmesan cheese plus additional for serving (optional)