Preheat your oven to 375°F (190°C) and lightly grease a small baking dish.
Cook the jumbo pasta shells in a large pot of boiling water until al dente according to package instructions, then drain and set aside to cool.
In a non-stick skillet over medium heat, cook the ground turkey with minced garlic and dried oregano until the meat is browned and fully cooked through.
Finely chop the fresh spinach and place it in a medium mixing bowl along with the cooked turkey, ricotta cheese, egg whites, parmesan cheese, sea salt, and black pepper.
Stir the mixture thoroughly until all ingredients are well combined and the spinach is evenly distributed.
Spread half of the marinara sauce across the bottom of the prepared baking dish.
Stuff each cooked pasta shell with a generous amount of the turkey and ricotta mixture, then arrange them in the baking dish.
Spoon the remaining marinara sauce over the top of the shells.
Cover the dish with foil and bake for 20 minutes, then remove the foil and bake for an additional 5 minutes until the sauce is bubbly and the shells are heated through.