Preheat your oven to 190°C (375°F).

Bring a large pot of salted water to a boil and cook the pasta shells according to package instructions until al dente, about 8-10 minutes. Drain and lay flat to cool.

In a skillet, heat olive oil over medium heat and sauté garlic for 1 minute. Add spinach and cook until wilted, about 3-4 minutes. Let cool, then combine with ricotta, mozzarella, Parmesan, and nutmeg.

Spread marinara sauce evenly in the baking dish. Stuff each shell with the filling, seam-side up, and pour remaining marinara sauce over them. Sprinkle with additional mozzarella.

Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 10 minutes until golden.

Let rest for 5 minutes, then garnish with basil or parsley before serving.