1. Bring a large pot of salted water to a boil and cook the jumbo pasta shells until al dente, 1-2 minutes less than package directions. Drain and set aside on a tray to prevent sticking.

2. Heat olive oil in a skillet over medium heat. Sauté onion and garlic until fragrant and translucent. Add ground turkey and cook until browned, breaking it apart with a spoon. Season with salt, pepper, and Italian seasoning.

3. Stir in fresh spinach and cook until wilted. Remove from heat and let the mixture cool slightly.

4. In a large bowl, mix the cooked turkey-spinach mixture with ricotta, 1 cup of mozzarella, and ½ cup of Parmesan until well combined.

5. Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish with olive oil. Spread 1 cup of marinara sauce over the bottom of the dish.

6. Stuff each pasta shell with the filling and arrange them in the dish. Spoon remaining marinara sauce over the top. Sprinkle with the remaining mozzarella and Parmesan.

7. Cover with foil and bake for 25 minutes. Remove foil and bake for another 10 minutes until bubbly and golden.

8. Let rest for 5–10 minutes before serving. Garnish with chopped parsley or basil if desired.