Preheat the oven to 350 degrees.
Add ground beef to a medium skillet, and sprinkle with some of the italian seasoning and garlic, then add salt and pepper. Brown the ground beef over medium heat, and drain grease.
While the meat is cooking, fill a large stock pot halfway with water, then add the pasta shells. Boil on high until pasta is al dente.
While the meat and pasta are cooking, chop the mushrooms
Add cottage cheese, 12 oz of the mozzarella cheese, mushrooms, the rest of the italian seasoning and garlic, along with a dash of salt and pepper to a large bowl. Once the ground beef is done, add that, along with 16 oz of the pasta sauce. Stir well.
Once the shells are cooked, drain, and rinse with cold water until they are not steaming hot, as you will be handling these with your hands.
Cover the bottom of a large casserole dish with a thin layer of pasta sauce.
Using a small spoon, fill the pasta shells, and set them gently into the baking dish, side by side.
Pour pasta sauce over the shells, as well as the remainder of the mozzarella cheese.
Bake for 30-40 minutes, until the cheese is melted and bubbly.
Serve hot, and sprinkle servings with parmesan cheese if desired.