Preheat the oven to 375°F. Bring a large pot of salted water to a boil and cook the jumbo shells about 1 minute less than al dente. Drain and rinse gently with cool water. Set aside.

Sauté the Spinach:

Heat olive oil in a skillet over medium heat. Add the garlic and cook for about 1 minute until fragrant. Add spinach and cook for 2–3 minutes, stirring, until wilted. Remove from heat and allow to cool.

Prepare the Cheese Filling:

In a large bowl, combine ricotta cheese with salt, pepper, basil, parsley, and oregano. Stir in half of the mozzarella cheese, most of the Parmesan (reserve some for topping), cream cheese, and egg until smooth. Fold in the cooled spinach mixture.

Assemble the Dish:

Spread half of the marinara sauce in the bottom of a 9×13-inch baking dish. Spoon the cheese filling into each shell and arrange them in the dish.

Top and Bake:

Spoon the remaining marinara sauce over the shells. Sprinkle with remaining mozzarella and reserved Parmesan cheese. Cover and bake for 20 minutes, then uncover and bake an additional 10 minutes until bubbly and lightly golden.

Serve:

Garnish with fresh parsley and serve warm.