While you are bringing the water to a boil, prepare the filling.
Beat the eggs in a bowl, and then add the ricotta cheese, mozzarella cheese, ½ cup Pecorino cheese, parsley, chopped spinach and the pinch of nutmeg.
Season with a little salt and pepper and combine all these ingredients with a large spoon.
When the pasta is ready, fill each shell with a large spoonful of the filling. You don’t want to over-stuff them but don’t be skimpy either.
In a baking dish big enough to hold all the shells, pour in some of the tomato sauce to coat the bottom of the dish. Add a layer of shells, then some more sauce and then another layer of shells. Top with a little more sauce.
Depending on the size of your baking dish, you’ll end up with two layers.
Top the shells with the remaining ¼ cup of Pecorino cheese and cover. If the baking dish doesn’t have a cover, use some aluminum foil.
Bake for about 35 minutes. When done, the pan will be hot and bubbly.
Remove the pan from the oven, remove the cover and let it sit for a couple of minutes to cool down a bit.
Using a large serving spoon, carefully serve the shells and serve with some fresh Italian bread.