Melt 4 tablespoons butter in heavy large pot over medium heat. Add onions and sauté until very tender and caramelized, about 25 minutes. Transfer onions to large bowl.
Melt remaining 4 tablespoons butter in same pot over medium-high heat. Add mushrooms and 1 tablespoon thyme; sauté until mushrooms are deep brown, about 12 minutes. Add to bowl with onions. Season with salt and pepper.
Bring broth, 1 tablespoon thyme, and 2 teaspoons sage to boil in heavy large deep saucepan. Mix in wild rice; return to boil. Reduce heat; cover and simmer 30 minutes.
Mix in white rice; cover and simmer until all rice is tender and almost all liquid is absorbed, about 18 minutes longer.
Stir in caramelized onions and mushrooms, remaining 1 tablespoon thyme, and 1 teaspoon sage. Stir in pears.
Cover and simmer 5 minutes, stirring often. Season with salt and pepper. Stir in 3/4 cup parsley.
To bake stuffing in turkey:
Loosely fill neck and main cavities of turkey with stuffing. Generously butter a baking dish. Spoon remaining stuffing into prepared dish. Cover with buttered foil, buttered side down.
Bake stuffing in dish along side turkey until heated through, about 25 minutes. Uncover stuffing. Bake until top of stuffing is slightly crisp and golden, about 15 minutes longer.
To bake all of stuffing in baking dish:
Preheat oven to 350°F. Generously butter 13x9x2-inch glass baking dish. Transfer stuffing to prepared dish. Cover with buttered foil, buttered side down. Bake until heated through, about 40 minutes. Uncover and bake until top is slightly crisp and golden, about 20 minutes longer.
Sprinkle remaining 1/4 cup chopped Italian parsley over stuffing and serve.
Makes 8 to 10 servings.