Preheat your oven to 375°F (190°C).
In a large pot of boiling salted water, cook the lasagna noodles according to package instructions until al dente. Drain and set aside.
In a mixing bowl, combine the ricotta cheese, egg, garlic powder, Italian seasoning, salt, and pepper. Mix until smooth.
Spread a thin layer of Alfredo sauce on the bottom of a 9x13 inch baking dish to prevent sticking.
Layer 3 lasagna noodles over the sauce, then spread half of the ricotta mixture on top of the noodles.
Add half of the shredded chicken, half of the spinach (if using), and one cup of mozzarella cheese on top.
Pour 1 cup of Alfredo sauce over the layers.
Repeat the layering process: 3 noodles, remaining ricotta mixture, remaining chicken, remaining spinach (if using), and another cup of mozzarella. Pour another cup of Alfredo sauce over this layer.
Top the final layer with the remaining 3 noodles, the rest of the Alfredo sauce, and sprinkle with the remaining mozzarella and Parmesan cheese.
Cover the dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.
Let the lasagna cool for 10 minutes before slicing. Serve warm.