Cook manicotti; drain. Mix onion, spinach, bouillon, garlic, thyme, Ricotta, eggs, Parmesan cheese, oregano and 1/2 the mushrooms. Fill manicotti shells with spinach mixture. Arrange in greased 9x13 baking dish. Pour tomato sauce and remaining mushrooms over manicotti. Sprinkle with oregano; cover with Mozzarella. Cover and cook at 350 degrees until hot and bubbly, about 25 minutes. ALTERNATE FILLING Brown meat in skillet; drain. Mix with all other ingredients. Stuff manicotti with meat mixture. Proceed as in first recipe.