Preheat your oven to 375°F (190°C).
Cook the jumbo pasta shells in a large pot of boiling salted water 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, breaking it into small crumbles.
Place the fresh baby spinach in a steamer basket for 2 minutes until wilted, then squeeze out all excess moisture and finely chop.
In a medium mixing bowl, combine the ricotta cheese, egg, chopped spinach, cooked ground turkey, sea salt, black pepper, garlic powder, and dried oregano.
Spread half of the marinara sauce onto the bottom of a small oven-safe baking dish.
Stuff each cooked pasta shell with a generous portion of the spinach-ricotta-turkey mixture and arrange them in the baking dish.
Spoon the remaining marinara sauce over the shells and sprinkle evenly with grated parmesan cheese.
Cover with foil and bake for 15 minutes, then remove the foil and bake for an additional 5-10 minutes until the sauce is bubbling and the cheese is lightly browned.