Preheat your oven to 375°F and lightly grease a small baking dish.
Cook the jumbo shells in a pot of boiling salted water until al dente, then drain and set aside.
In a skillet over medium heat, sauté the ground turkey and minced garlic in olive oil until the turkey is fully browned.
Stir in the marinara sauce, dried oregano, and garlic powder, then let the sauce simmer for 5 minutes.
Steam the baby spinach until wilted, squeeze out all excess liquid thoroughly, and finely chop.
In a medium bowl, combine the chopped spinach, ricotta cheese, egg whites, sea salt, and black pepper until smooth.
Spread a thin layer of the turkey marinara sauce on the bottom of the prepared baking dish.
Generously stuff each cooked shell with the spinach-ricotta mixture and arrange them in the dish.
Spoon the remaining turkey sauce over the shells and sprinkle with the parmesan cheese.
Bake for 20 minutes until the sauce is bubbly and the cheese is lightly golden.