In a food processor, pulse the blanched spinach until finely chopped. Add the flour, eggs, Parmesan cheese, salt, black pepper, and nutmeg to the food processor and pulse until the dough comes together.

Remove the dough from the food processor and knead it on a floured surface until it becomes smooth and elastic. Cover the dough with a damp cloth and let it rest for 30 minutes.

While the dough is resting, mix together the ricotta cheese, mozzarella cheese, basil, and garlic in a bowl.

Roll out the dough until it is thin and cut out circles using a cookie cutter. Place a spoonful of the cheese mixture in the center of each circle of dough.

Fold the dough over the filling and press the edges together to seal the cappellacci. Repeat with the remaining dough and filling.

Bring a large pot of salted water to a boil. Add the cappellacci to the water and cook for 3-4 minutes or until they float to the top.

While the cappellacci are cooking, melt the butter in a small saucepan over low heat. Add the Parmesan cheese and stir until it has melted and the sauce is smooth.