Step 1: Cook the Pasta

• Bring a large pot of salted water to a boil.
• Add the jumbo pasta shells and cook according to package instructions until al dente.
• Drain and set aside to cool slightly.

Step 2: Prepare the Filling

• In a large bowl, combine ricotta cheese, shredded mozzarella, grated Parmesan, spinach, egg, garlic powder, Italian seasoning, salt, and pepper.
• Mix until well combined.

Step 3: Stuff the Pasta

• Carefully stuff each cooked pasta shell with the cheese and spinach mixture.
• Use a spoon or piping bag for easier filling.

Step 4: Prepare the Sauce

• In a saucepan, heat the marinara sauce over medium heat.
• Stir in dried basil and red pepper flakes if using.

Step 5: Assemble the Dish

• In a baking dish, spread a thin layer of marinara sauce on the bottom.
• Arrange the stuffed pasta shells on top, then pour the remaining marinara sauce over the shells.
• Sprinkle shredded mozzarella cheese over the top.

Step 6: Bake

• Cover the baking dish with aluminum foil and bake in a preheated oven at 375°F (190°C) for 20 minutes.
• Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.

Step 7: Serve

• Remove from the oven and let cool for a few minutes.
• Garnish with fresh basil or parsley before serving.