Preheat oven to 350°.
Heat a medium nonstick skillet coated with cooking spray over medium-high heat. Add onion and mushrooms; sauté 5 minutes or until tender. Set aside.
Beat the cream cheese at medium speed of a mixer until smooth; add the cottage cheese, sour cream, 1/2 cup of Parmesan cheese, and eggs, beating well. Add the onion mixture and spinach, and beat well.
Spread 1/2 cup of the spinach mixture in the bottom of a 13 x9-inch baking dish coated with cooking spray. Arrange 3 noodles over the spinach mixture; top with 1 cup of spinach mixture, 3/4 cup of pasta sauce, 1/4 cup of mozzarella cheese, and 1 tablespoon of Parmesan cheese. Repeat the layers, ending with Parmesan cheese.
Cover and bake at 350° for 50 minutes. Sprinkle with cheddar cheese; bake, uncovered, an additional 10 minutes. Let stand 10 minutes.