Preheat oven to 400º
Prepare the jumbo shells according to the package.
Mix together the cottage cheese, spinach, 1/2 cup mozzarella cheese and parmesan. Feel free to add in some salt and pepper, Italian seasoning, garlic pepper and onion powder with the mixture.
Combine the spaghetti sauce and mushrooms and spread half of it into a 9x13 baking dish.
Once the shells have cooked and cooled a bit, fill each shell with the mixture. Lay the shells in the baking dish.
Top with the remaining sauce.
Cover the dish with foil that has been sprayed with Pam - so that it doesn't stick.
Bake 25 minutes.
Remove from the oven, top with remaining mozzarella cheese (more if you like it cheesy).
Bake, uncovered, for 3-5 minutes or until the cheese is melted.