Preheat the oven to 375ºF.
Cook the lasagna noodles according to the package instructions, then drain and set aside.
In a skillet over medium heat, brown the Italian sausage or ground beef until fully cooked. Drain off any excess fat. Stir in the spaghetti sauce, tomato sauce, and Italian seasoning. Let the mixture simmer over low heat for 5 to 10 minutes until slightly thickened, then remove from heat and set aside.
In a large mixing bowl, combine the cottage cheese, softened cream cheese, sour cream, beaten egg, and dried parsley. Mix until smooth and well blended, then set aside.
Lightly coat a 9×13-inch baking dish with non-stick cooking spray. Spread 1 cup of the meat sauce evenly across the bottom of the dish. Place 6 lasagna noodles on top, overlapping slightly to cover the surface.
Spread half of the cheese mixture over the noodles. Layer with one-third of the mozzarella cheese slices. Spoon half of the remaining meat sauce over the cheese and sprinkle with ¼ cup of grated parmesan.
Repeat the layers starting with the remaining 6 noodles, followed by the rest of the cheese mixture, another third of the mozzarella, the remaining meat sauce, and the last ¼ cup of parmesan. Finish by topping with the remaining mozzarella slices.
Cover the pan with foil and bake for 25 minutes. Remove the foil and continue baking uncovered for an additional 30 minutes, or until the lasagna is hot and bubbly. Allow it to rest for 15 minutes before serving to help it set.