- Preheat oven to 375°F. Spread bread on large rimmed baking sheet. Bake until bread is dry, about 15 minutes. Cool. 
- Melt 10 tablespoons butter in heavy large skillet over medium heat. Add mushrooms and leeks and saute for 6 minutes. Add green onions, celery, all the herbs, garlic, salt and pepper and sauté until celery is tender, 6 to 8 minutes. 
- Preheat oven to 375°F. Generously butter 13x9x2-inch glass baking dish. Place bread cubes in very large bowl. Add warm vegetable mixture; toss to combine. 
- Whisk eggs and 3/4 cup broth in medium bowl. Add egg mixture to stuffing and toss to coat. Mix in Parmesan. 
- Add more broth (about 1/2 to 3/4 cup) to stuffing if dry. Transfer to dish. Cover with buttered foil. Bake 30 minutes. Remove foil; bake until golden, about 30 minutes.