Cook the jumbo pasta shells according to package instructions until al dente. Drain and set aside.
In a mixing bowl, combine ricotta cheese, chopped spinach, 3/4 cup mozzarella cheese, Parmesan cheese, egg, garlic powder, salt, and pepper. Mix until well combined.
Stuff each cooked shell with the cheese mixture and place in a greased baking dish.
Spoon marinara sauce over the stuffed shells and sprinkle remaining mozzarella on top.
Cover the dish with foil and bake for 20 minutes. Remove foil and bake for an additional 5 minutes until cheese is bubbly.
Let it cool for a few minutes before serving.
Notes
Drizzle with olive oil before serving for added richness. Serve with a side salad to complete the meal.