Preheat your oven to 180°C (350°F).
Cook the pasta shells in boiling salted water until just al dente, about 8 minutes. Drain and set aside to cool slightly.
In a mixing bowl, combine ricotta, shredded mozzarella, chopped spinach, minced garlic, and a pinch of nutmeg. Mix until well blended and creamy.
Using a spoon or piping bag, fill each shell generously with the cheesy mixture, pressing down to fill completely and ensuring no air pockets.
Arrange the stuffed shells in a baking dish, pressing them gently into place. Spoon any leftover filling over the top for extra cheesy goodness.
Pour marinara sauce over the shells, covering them evenly but leaving some exposed edges for bubbling.
Sprinkle additional mozzarella cheese on top and add a dash of red pepper flakes for a spicy kick.
Bake uncovered in the oven for 25-30 minutes until bubbling and golden around the edges, with melted cheese on top.
Once baked, remove from the oven and let rest for about 5 minutes. The filling will set slightly, making it easier to serve.
Serve hot, with the cheese oozing from the shells and the spicy marinara complementing each bite.
