Preheat the oven to 375°F (190°C).

Cook the lasagna noodles according to package instructions until al dente. Drain and set aside.

In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant.

Add the spinach to the skillet and cook until wilted (if using fresh) or heated through (if using frozen). Season with salt, pepper, and Italian seasoning, if desired. Remove from heat.

In a mixing bowl, combine the ricotta cheese, egg, and half of the Parmesan cheese. Mix well and season with salt and pepper.

In the prepared baking dish, spread a thin layer of marinara sauce on the bottom.

Layer 4 lasagna noodles over the sauce, followed by half of the ricotta mixture, half of the spinach mixture, and a third of the mozzarella cheese. Add another layer of marinara sauce.

Repeat the layering process with another 4 lasagna noodles, the remaining ricotta mixture, the remaining spinach, and another third of the mozzarella cheese. Finish with a layer of marinara sauce and the remaining noodles on top.

Spread any remaining marinara sauce over the final layer of noodles, then sprinkle with the remaining mozzarella and Parmesan cheese.

Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 20 minutes until the cheese is bubbly and golden.

Allow the lasagna to cool for 10 minutes before slicing and serving.

Customize the recipe by adding other vegetables like mushrooms or zucchini if desired.