Prepare the filling by mixing the spinach, ricotta, shredded cheese, and minced garlic. Stir well. Refrigerate for 1 hour.

Meanwhile, fill a large pot with water and bring it to a boil. Add the conchiglioni pasta and cook until halfway done.

Drain the pasta and let it cool. Then, fill each shell with the prepared filling using your hands.

In a baking dish, spread a layer of warmed tomato puree. Arrange the stuffed conchiglioni on top, then add more tomato puree over them.

Bake in the oven at 400°F (200°C) for 30 minutes.