Directions:

Preheat oven to 375°F (190°C). Cook pasta shells according to package instructions; drain and cool.
In a skillet, brown ground beef over medium heat. Drain excess fat and mix in marinara sauce. Remove from heat.
In a bowl, combine ricotta, egg, Italian seasoning, salt, and pepper.
Fill each pasta shell with the ricotta mixture, then place in a baking dish. Top with the beef mixture and sprinkle with mozzarella and Parmesan.
Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 10 minutes until cheese is bubbly.