Melt butter, sauté garlic, add cream, whisk in Parmesan, season with salt, pepper, and nutmeg.
Mix ricotta, mozzarella, Parmesan, egg, and parsley in a large bowl.
Preheat oven to 375°F (190°C), grease a 9x13-inch baking dish, and layer sauce, noodles, ricotta mix, chicken, spinach. Repeat layers.
Top with noodles, sauce, and mozzarella. Cover with foil and bake for 35 minutes, then uncover and bake another 15 minutes until golden.
Rest 15 minutes before slicing. Garnish with fresh parsley.