Preheat oven to 375 F. Cook lasagna noodles according to package directions, drain. Heat olive oil in a large saucepan over medium heat. Add in fresh spinach leaves and cook until wilted.
In a medium bowl, combine the ricotta cheese with the wilted spinach, grated parmesan cheese and egg. Spread a thin layer of marinara sauce in the bottom of a large baking dish. Layer with 4-5 lasagna noodles, 1/4 of the ricotta spinach mixture, 1/4 of the marinara sauce and 1 cup of the shredded mozzarella cheese.
Repeat the layers 4 times, ending in the lasagana noodles, ricotta spinach mixture, marinara sauce and the remaining mozzarella cheese. Cover with foil. Bake for 30-35 minutes. Uncover and bake for another 15 minutes.
