Instructions

• Position an oven rack in the top third of the oven and preheat the oven to 375°F (190°C).
• Pour the jar of marinara sauce (24 ounces) into the bottom of a 9×13-inch casserole dish and spread it evenly.
• Bring a large pot of water to a rolling boil. Add the 24 uncooked jumbo shells and cook them for 1 minute less than the time indicated on the package. Drain the shells in a colander and let them sit until they are cool enough to handle.
• While the shells cook (or while they are cooling), make the filling: if the 16 ounces of frozen spinach is not yet thawed, thaw it completely. Squeeze or press the thawed spinach to remove as much liquid as possible.
• Transfer the drained spinach to a mixing bowl. Add the 15 ounces ricotta cheese, 1 cup freshly grated Parmesan cheese, 1 egg, 1/2 teaspoon salt, pepper to taste, 1/2 teaspoon Italian seasoning, and 1/2 teaspoon garlic powder.
• Stir the filling ingredients until they are well combined and evenly mixed.
• Using a small spoon, fill each cooked jumbo shell with the spinach–ricotta mixture. Place each filled shell into the marinara in the casserole dish, arranging them in a single layer (seam-side up if possible).
• Once all shells are in the dish, sprinkle 2 cups shredded mozzarella cheese evenly over the top of the shells.
• Cover the casserole dish tightly with foil and bake in the preheated oven for 30 minutes.
• Remove the foil and switch the oven to broil. Broil the casserole for a few minutes, watching carefully, until the cheese is browned to your liking.
• Remove from the oven and serve immediately. Garnish with fresh basil and/or chopped parsley if using, and season with extra salt and pepper to taste.