Preheat oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.
Cook jumbo pasta shells in a large pot of boiling salted water according to package directions for al dente; drain and set aside to cool.
In a large mixing bowl, combine shredded chicken, 1 cup of the blended cottage cheese, 1/4 cup Parmesan cheese, egg, chopped spinach, salt, pepper, and Italian seasoning.
In a separate small bowl, whisk together the remaining 1 cup of blended cottage cheese, skim milk, garlic, and the remaining 1/4 cup Parmesan cheese to create the Alfredo sauce.
Spread approximately 1/4 cup of the Alfredo sauce onto the bottom of the prepared baking dish.
Stuff each cooked pasta shell generously with the chicken and cheese mixture and arrange them in the baking dish.
Pour the remaining Alfredo sauce over the stuffed shells and sprinkle evenly with shredded mozzarella cheese.
Cover the dish with foil and bake for 20 minutes; remove foil and bake for an additional 10 minutes or until the cheese is melted and bubbly.
Let rest for 5 minutes before serving.