Bring a large pot of salted water to a boil, and gently add the jumbo pasta shells. Cook for 8–10 minutes, or until al dente, stirring occasionally to prevent sticking. Once cooked, drain the shells in a colander and let them cool slightly.

In a mixing bowl, combine the ricotta cheese, ½ cup of shredded mozzarella, grated Parmesan, and the egg until the mixture is smooth and well blended.

In a skillet, heat 1 tablespoon of olive oil over medium heat. Add minced garlic and sauté for about 30 seconds until fragrant, then add the fresh spinach and cook for 2–3 minutes until it wilts.

Carefully add the sautéed spinach to the ricotta mixture. Stir gently until the spinach is evenly distributed.

Sprinkle in Italian seasoning, salt, and black pepper, mixing well to ensure that each bite of the filling is flavorful.

Preheat your oven to 375°F (190°C).

Spread 1 cup of marinara sauce across the bottom of a baking dish. Stuff each cooked shell with about 2 tablespoons of the filling and arrange them in the dish.

Ladle the remaining marinara sauce over the stuffed shells and sprinkle the rest of the shredded mozzarella on top. Cover with foil and bake for 20 minutes.

Remove the foil and continue baking for an additional 10 minutes, or until the cheese is bubbly and slightly golden.

Allow the stuffed shells to rest for 5 minutes before serving. Garnish with fresh basil if desired.