1. Preheat the oven to 375°F and lightly grease a 9×13-inch baking dish.

2. Cook the jumbo pasta shells in salted boiling water until just al dente, then drain and let them cool enough to handle.

3. In a large bowl, mix the ricotta cheese, 1 cup mozzarella, 1/4 cup Parmesan, chopped sun-dried tomatoes, garlic, egg, Italian seasoning, salt, and black pepper until well combined.

4. Stir the heavy cream into the marinara sauce.

5. Spread about 1 cup of the creamy marinara sauce across the bottom of the prepared baking dish.

6. Spoon the ricotta filling into each cooked shell and arrange the filled shells in the dish open-side up.

7. Spoon the remaining sauce around and lightly over the shells.

8. Sprinkle the tops with the remaining 1 cup mozzarella and 1/4 cup Parmesan.

9. Cover with foil and bake for 25 minutes.

10. Remove the foil and bake for 10 more minutes, until the cheese is melted and bubbly.

11. Let the dish rest for 5 minutes, then sprinkle with chopped parsley and serve.