To prepare the jumbo shells, cook them according to the guidelines provided on the package, then drain the water and wash them well using cold water.
Merge the ricotta cheese, spinach, Parmesan cheese, egg, garlic, salt, and pepper together in a big bowl and stir until they are uniformly combined.
Before starting to bake, ensure that the oven is preheated to 375°F, and then apply a layer of marinara sauce on the bottom of a 9×13-inch baking dish.
Fill each oversized shell with the ricotta mixture, then position them in the baking tray.
Once the shells are filled, sprinkle them with shredded mozzarella cheese, and then cover them with the remaining marinara sauce.
Cover the dish with foil and bake it for 25 minutes, then uncover it and continue baking for 10-15 minutes until the cheese has melted and is bubbling.
Cooling the shells for a few minutes is recommended before they are served.
