Preheat your oven to 375°F (190°C).
Bring a large pot of salted water to a boil and cook the jumbo shells according to package directions until al dente, then drain and set aside.
In a non-stick skillet over medium heat, cook the ground turkey until browned and fully cooked through.
Roughly chop the fresh spinach and stir it into the hot turkey until it is completely wilted.
In a medium bowl, combine the turkey and spinach with the ricotta cheese, egg white, garlic powder, oregano, sea salt, and black pepper.
Spread half of the marinara sauce across the bottom of a small oven-safe baking dish.
Fill each cooked pasta shell with a generous amount of the turkey and ricotta mixture and place them in the baking dish.
Spoon the remaining marinara sauce over the shells and sprinkle with the parmesan cheese.
Cover the dish with foil and bake for 15 minutes, then remove the foil and bake for an additional 5 minutes until the sauce is bubbling and the cheese is melted.