Preheat oven to 350°F
Boil noodles to al-dente, drain and cool till easy to handle.
Brown sausage, then saute onions, mushrooms, and garlic till soft. Stir in seasoning.
Whisk eggs, mix in ricotta. Stir in cheeses and spinach. Mix in cooled sausage, onion mixture.
Stuff the shells with mixture and place in baking dish with 2 cups of Alfredo sauce in bottom of dish.
Cover with remaining sauce and sprinkle with more grated cheese & seasoning if desired.
Bake 10-15 minutes covered with foil, then remove foil and bake another 5-10 minutes until top is slightly browned.