Preheat the oven to 350°F. In a medium-sized bowl, stir the egg with the ricotta cheese, 1-½ cups of the mozzarella cheese, crumbled feta, grated Parmesan, chopped fresh basil, minced garlic and pepper.
Spread ½ cup of the pasta sauce into a greased 13x9-inch baking dish. Layer three lasagna noodles onto the sauce, followed by ¾ cup of the ricotta mixture, 1 cup of the baby spinach, and ⅔ cup of the pasta sauce. Repeat the layers twice. Finish by sprinkling the remaining mozzarella cheese on top.
Bake, covered, for 35 minutes. Remove the cover, and continue baking until the lasagna is heated and the cheese is melted for 10 to 15 minutes. Let the lasagna rest for five minutes. Slice and serve.
