Begin by cooking large pasta shells in a pot of generously salted boiling water. Follow the package instructions and cook until al dente, usually about 8 to 10 minutes. Once done, drain the shells and spread them out on a flat surface to cool, ensuring they don’t stick together while you prepare the filling.

In a mixing bowl, combine well-drained ricotta cheese, chopped fresh or thawed spinach, half of the mozzarella, grated Parmesan, garlic powder, onion powder, and a sprinkle of salt and pepper. If using, mix in the egg for added binding. Stir gently until just combined, creating a creamy and vibrant filling.

Take each cooled pasta shell and carefully spoon in the ricotta filling using a small spoon or piping bag. Be cautious not to overstuff them, as they will expand during baking. Arrange the stuffed shells in a greased baking dish.

Preheat your oven to 375°F (190°C). Pour marinara sauce evenly over the stuffed shells. Then, sprinkle the remaining mozzarella cheese on top.

Cover the baking dish with aluminum foil and place it in the preheated oven. Bake for about 25 minutes, or until the sauce is bubbling. Remove the foil during the last 10 minutes for a crispy top.

Once baked, carefully remove the dish from the oven and let it rest for about 10 minutes. Garnish with fresh basil, if desired, and enjoy!