We smash our garlic cloves with the side of our knife, being careful of the sharp blade. We discard the peels and mince with some kosher salt. We add the teaspoon of garlic to a large saute pan, pour in the olive oil, and heat over medium-low. When the garlic begins to sizzle, we add the baby spinach and cook for a few minutes, tossing with tongs, over medium heat. When the spinach is just wilted, we add some salt and pepper and then we spread the spinach mixture on a dinner plate to cool.
We are now ready to combine the cheeses. Over a piece of wax paper, we grate the mozzarella using our box grater. We put some of the shredded mozzarella into a 1-cup measuring cup. The rest we put into a ¼ cup measuring cup and reserve for the top of the baked pasta. We have a total of 1¼ cups of mozzarella (we also ate some!) We combine the 1-cup shredded mozzarella, Locatelli, and ricotta cheese in a large bowl.
Meanwhile, the pasta water has come to a boil. We add some salt to the water and the jumbo shells. We stir carefully and cook for 9 minutes (a minute shy of the package directions for al dente.)
While the pasta is cooking, we pre-heat the oven to 375 degrees and start heating our prepared tomato sauce. Then we pulse our spinach mixture in our food processor to chop. We add the spinach, a few fresh gratings of nutmeg, and the fresh parsley to the cheese bowl. We also add some freshly ground black pepper, stir, and taste for seasoning (it’s delicious!). When the sauce is hot, we coat the bottom of a 13 × 9 inch glass baking pan with ½ cup tomato sauce.
Our shells have cooked enough, so we drain them in a colander. Using tongs, we place each shell in the baking dish, facing up so that we can fill them. We are careful to remove as much water as possible before adding them to the pan. When we have fit as many as we can in one layer, we rinse the rest of the shells with cool water and refrigerate, covered for another day. We place a heaping teaspoonful of the spinach-cheese filling inside each shell. We are able to fill 19 of the shells with our spinach-cheese mixture. The rest we leave unfilled for the kids. We top the shells with 1½ cups of sauce and sprinkle on the rest of the mozzarella. We place the pan, covered with foil, into the oven and bake for 25 minutes.
We remove the bubbling pan from the oven and, after a couple of minutes, carefully serve the stuffed shells with additional hot tomato sauce and grated Locatelli.