Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Prepare Chicken: Heat olive oil in a skillet over medium heat. Add cooked chicken, garlic powder, Italian seasoning, salt, and pepper. Toss to coat and heat through.
Make Cheese Filling: In a medium bowl, combine ricotta cheese, Parmesan cheese, egg, nutmeg, garlic powder, and salt. Mix well.
Assemble Lasagna: Spread a thin layer of Alfredo sauce on the bottom of the prepared baking dish.
Layer 1: Arrange 3 lasagna noodles over the sauce.
Layer 2: Spread half of the ricotta cheese mixture over the noodles.
Layer 3: Top with half of the seasoned chicken and 1/3 of the mozzarella cheese.
Layer 4: Drizzle with 1/3 of the remaining Alfredo sauce.
Repeat: Repeat layers 1-4 one more time.
Top Layer: Arrange the final 3 noodles on top. Spread with the remaining Alfredo sauce and sprinkle with the remaining mozzarella cheese.
Bake: Cover the dish with aluminum foil and bake for 30 minutes.
Uncover: Remove the foil and bake for an additional 15-20 minutes, or until the cheese is melted and bubbly and the lasagna is heated through.
Rest: Let the lasagna rest for 10-15 minutes before slicing and serving.
Garnish: Garnish with fresh parsley, if desired.