In a large frying pan brown the meat. Crumble it into small pieces (I use a potato masher to do this) while cooking. Remove from the heat and add the alfredo sauce and ½ teaspoon salt. Set aside.
Preheat oven to 350 if baking immediately (you can also refrigerate for a day or two before baking).
In a separate bowl whisk together the ricotta, egg, ½ teaspoon salt, garlic, and onion.
Spread half the meat in the bottom of a large casserole dish. Top with half the ricotta and then half the spinach. Sprinkle half the mozzarella on top. Repeat the layers: meat, ricotta, spinach, and the finish with the rest of the mozzarella on top.
Bake for 35-40 minutes until the cheese on top is golden and bubble