Step 1: Cook the Pasta Shells

Bring a large pot of salted water to a boil. Add the jumbo pasta shells and cook them according to the package instructions until they are al dente. This means they should be firm but fully cooked. Overcooking the pasta can make the shells too soft, making them difficult to stuff. Once cooked, drain the shells and rinse them with cool water to stop the cooking process. Set them aside.

Step 2: Prepare the Spinach and Garlic

If using fresh spinach, wash it thoroughly, dry it, and chop it into small pieces. Heat one tablespoon of olive oil in a skillet over medium heat. Add the minced garlic and sauté for about 30 seconds until fragrant. Then, add the spinach and cook until it wilts, which should take about two minutes. If using frozen spinach, simply heat it through and drain any excess liquid. Season the spinach lightly with salt and pepper.

Step 3: Make the Cheese Filling

In a mixing bowl, combine the ricotta cheese, shredded mozzarella, grated parmesan, egg, nutmeg (if using), and the cooked spinach mixture. If adding ground chicken or beef, stir it into the filling at this stage. Mix until all ingredients are well incorporated. The consistency should be thick but spreadable.

Step 4: Assemble the Dish

Preheat the oven to 375°F (190°C). Spread a layer of marinara sauce on the bottom of a baking dish to prevent the shells from sticking and to add extra moisture. Carefully stuff each pasta shell with the ricotta and spinach mixture, using a spoon or piping bag for ease. Place the stuffed shells in the baking dish with the open side facing up. Pour the remaining marinara sauce over the shells, ensuring they are well covered. Sprinkle additional mozzarella on top for a golden, cheesy finish.

Step 5: Bake the Stuffed Shells

Cover the baking dish with aluminum foil and bake for 25 minutes. This allows the cheese to melt and the flavors to blend. Remove the foil and continue baking for another 10 minutes until the cheese is bubbly and slightly golden. If you prefer a crispier top, broil the dish for the final two minutes.

Step 6: Garnish and Serve

Once baked, remove the dish from the oven and let it rest for a few minutes before serving. Garnish with fresh basil or parsley for added color and flavor.