Heat oven to 375°F. Cook and drain pasta as directed on package. Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Spread 1/3 cup of the pasta sauce over bottom of baking dish.
In medium bowl, mix 1 cup of the mozzarella cheese, the cottage cheese, prosciutto and spinach. Spoon scant 2 tablespoons mixture into each shell. Arrange filled shells in baking dish. Pour remaining pasta sauce over stuffed shells. Sprinkle remaining 2 cups mozzarella cheese evenly over sauce.
Cover dish with foil. Bake 30 to 40 minutes or until thoroughly heated. Sprinkle with basil.