Cook lasagna noodles and drain. Cool under cold running water; drain again and set aside. Preheat oven to 350 degrees. In a large saucepan, cook spinach over medium-high heat, stirring frequently until leaves are limp 2-3 minutes. Drain spinach in a colander and press excess water out with the back of a wooden spoon. When cool enough to handle, squeeze dry. Turn spinach out onto a cutting surface and chop fine.
In a large bowl, combine spinach, ricotta, egg yolks, 3/4 cup Parmesan cheese, salt, pepper and nutmeg. Mix with a wooden spoon until well blended. In a greased 13x9 inch baking dish, alternately layer spinach pasta with spinach ricotta mixture and mozzarella, making a total four layers. Cover with foil and bake 25 minutes. Uncover and bake 10 minutes longer, or until tomato sauce and remaining Parmesan cheese on the side.