Preheat your oven to 375°F (190°C). Cook the jumbo pasta shells according to the package instructions until they are al dente. Drain the pasta and set aside to cool slightly.

In a large skillet, heat a drizzle of olive oil over medium heat. Add the ground turkey and cook, breaking it up with a spoon, until browned, about 6-8 minutes.

Stir in the chopped spinach, garlic powder, salt, and pepper. Cook until the spinach wilts, about 2-3 minutes.

In a mixing bowl, combine the turkey and spinach mixture with the ricotta cheese and half of the mozzarella cheese. Mix well to combine.

Carefully stuff each cooked pasta shell with the turkey-spinach mixture.

Spread a layer of marinara sauce in the bottom of a baking dish. Place the stuffed shells on top, pour the remaining marinara sauce over the shells, and sprinkle with the remaining mozzarella and Parmesan cheese.

Cover the dish with foil and bake for 25 minutes. Remove the foil and bake for another 10 minutes, until the cheese is bubbly and slightly golden.

Once baked, let the dish cool for a few moments before serving. Enjoy your meal while it's warm.