Preheat your oven to 375°F (190°C).
Cook the jumbo pasta shells in a large pot of boiling salted water until al dente, then drain and set aside to cool.
Heat the olive oil in a skillet over medium heat and brown the ground turkey until no longer pink.
Add the chopped fresh spinach to the skillet and sauté for 1-2 minutes until wilted, then remove from heat.
In a mixing bowl, combine the ricotta cheese, half of a beaten egg, parmesan, garlic powder, sea salt, and black pepper.
Fold the cooked turkey and spinach mixture into the ricotta mixture until well combined.
Spread half of the marinara sauce across the bottom of a small oven-safe baking dish.
Fill each cooked pasta shell generously with the turkey and ricotta mixture and arrange them in the baking dish.
Top the shells with the remaining marinara sauce and sprinkle with shredded mozzarella 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 and bubbly.