Blanch the ravioli a few at a time in salted water for one or two minutes and drain on an oiled plate so they don't stick. They should not be cooked all the way.
Pour 1 1/2 cups sauce into a 9 x 13" pan and line the spinach leaves over top. Place ravioli on top of spinach and top each ravioli with a slice of mozzarella. Spoon remaining sauce over top of cheese.
Cover pan with plastic wrap and then cover with foil very tightly. You can stow this in the refrigerator for up to 24 hours. Bring to room temperature while you pre-heat the oven.
Bake about 45 minutes to an hour or until the ravioli are hot throughout. Time depends on how big, or cold the ravioli are.
When the ravioli are done just uncover for a few minutes and sprinkle with parmesan cheese and let melt in the oven, about 5 minutes. Watch it so it does not burn. Sprinkle with basil.