1. Preheat your oven to 375°F (190°C). Grease a large baking dish and set aside.
2. Cook the pasta shells in boiling salted water until al dente. Drain and rinse under cold water to stop the cooking process. Set aside.
3. In a large skillet, heat olive oil over medium heat. Add the ground beef, onion, and garlic. Cook until the beef is browned and the onion is translucent, about 8 minutes.
4. Stir in the Italian herbs, salt, and pepper, then remove from heat. Let it cool slightly.
5. In a large bowl, mix together the ricotta, Parmesan, and egg until well combined. Gently fold in the beef mixture.
6. Spread 1 cup of marinara sauce over the bottom of the prepared baking dish.
7. Stuff each shell with a generous spoonful of the beef and ricotta mixture and arrange them in the baking dish.
8. Pour the remaining marinara sauce over the shells and sprinkle with mozzarella cheese.
9. Cover with foil and bake for 25 minutes, then remove the foil and bake for another 10 minutes, or until the cheese is bubbly and golden.
10. Garnish with fresh basil leaves before serving.

Remember, cooking is as much about intuition as it is about instructions. Feel free to adjust the seasonings to suit your taste. My dad always said a dish should tell your own story, and I couldn’t agree more.