Preheat your oven to 375°F.
Cook the jumbo pasta shells in a large pot of boiling salted water until al dente, then drain and set aside to cool.
In a non-stick skillet over medium heat, cook the ground turkey until browned and fully cooked through, then set aside.
Steam the fresh baby spinach until wilted, squeeze out all excess moisture using a clean kitchen towel, and chop it finely.
In a medium mixing bowl, combine the cooked turkey, ricotta cheese, chopped spinach, egg white, garlic powder, dried oregano, sea salt, and black pepper.
Spread half of the marinara sauce evenly across the bottom of a small baking dish.
Stuff each cooked pasta shell generously with the turkey and ricotta mixture and place them in the baking dish.
Top the shells with the remaining marinara sauce and sprinkle with shredded mozzarella and grated parmesan cheese.
Cover the dish with foil and bake for 20 minutes.
Remove the foil and bake for an additional 5-10 minutes until the cheese is melted, bubbly, and slightly golden.