Carmelized Onion Meatball Lasagna
Preheat oven to 350 degrees.
In a bowl, combine the ricotta, spinach, cheese, egg, salt and pepper. Set aside.
To make the white sauce: Melt the butter in a large saucepan over medium high heat. Add the flour and cook, stirring, for 2 minutes. Add the milk and stir to combine. Bring to a boil, then reduce heat to a simmer and continue to cook 3-5 minutes until the sauce begins to thicken. Heavily season with salt, pepper and nutmeg.
To assemble, spoon some of the sauce into the bottom of a large rectangular baking dish. Place a single layer of noodles in the bottom of the dish. Cover completely with a quarter of the white sauce. Layer in a third of the ricotta mixture, and then a third of the meatballs. Top with a quarter of the cheese, and then repeat until you have three layers. Top the final layer with the remaining white sauce and cheese. Cover with foil and bake for 30 minutes. Remove the foil bake for 20 more minutes. Allow to rest 10 minutes before cutting and serving.