1. Bring a large pot of salted water to a boil and cook the jumbo pasta shells until just al dente. Drain and let them cool enough to handle.

2. In a large mixing bowl, combine the ricotta cheese, cream cheese, 1 cup of mozzarella, 1/4 cup of Parmesan, chopped spinach, garlic, Italian seasoning, salt, black pepper, and 1/2 cup of the chopped sun-dried tomatoes. Mix until smooth and evenly combined.

3. In a baking dish, spread the marinara sauce and heavy cream together across the bottom to create a creamy base.

4. Spoon the ricotta mixture into each cooked shell and arrange the stuffed shells in a single layer in the baking dish.

5. Top the shells with the remaining 1 cup mozzarella, remaining 1/4 cup Parmesan, and the remaining 1/2 cup sun-dried tomatoes.

6. Bake at 375°F for 25 to 30 minutes, until the cheese is melted and bubbly and the shells are heated through.

7. Remove from the oven, let rest for 5 minutes, then sprinkle with fresh parsley before serving.