Bring a large pot of salted water to a boil and cook the jumbo pasta shells according to package directions until just al dente. Drain and rinse under cold water to stop the cooking, then set aside.

In a mixing bowl, combine the ricotta cheese, chopped spinach, chopped artichoke hearts, minced garlic, Italian seasoning, and half of the Parmesan cheese. Add salt and pepper to taste and stir until evenly mixed.

Spread 1 cup of marinara sauce across the bottom of a baking dish. Spoon the spinach artichoke filling into each cooked shell and arrange the filled shells in a single layer over the sauce.

Pour the remaining cup of marinara sauce over the tops of the shells. Sprinkle the shredded mozzarella and the remaining Parmesan evenly across the surface.

Cover the dish tightly with foil and refrigerate until ready to bake. When ready, bake at 375°F for 25 to 30 minutes until the cheese is melted and the sauce is bubbling. Remove the foil for the last 5 minutes if you want a lightly browned top.