Preheat the oven to 375 degrees Fahrenheit.
In a large bowl, combine a beaten egg, ricotta cheese, 2 cups of mozzarella, ½ cup of Parmesan cheese, minced onion, minced garlic, thawed spinach, and Italian seasoning. Mix together well until all the ingredients are well incorporated.
In one 9 x 11 pan or two 8x8 pans spread ½ cup of sauce on the bottom of the pan.
Layer in the order of 2 uncooked lasagne noodles, ⅓ part of the ricotta mixture, ½ cup of mozzarella cheese, ½ cup sauce, and then repeat two more times. Top the last noodle with the remainder of the sauce followed by mozzarella and parmesan cheese.
Bake covered with foil for 20 minutes. Take the foil off and place back in the oven for an additional 5 minutes to brown and crisp the cheese.