After an hour and a half, we start on our filling. In a large saute pan we heat the olive oil over medium-low heat. We add our onions and cook, stirring occasionally, for about 10 minutes. We want them tender and golden. While the onions are cooking, we mince the garlic with a little kosher salt. We add the garlic when the onions are ready and cook for another minute. Lastly, we add the baby spinach and cook for a few minutes over medium heat. When the spinach is just wilted, we spread the spinach-onion mixture on a dinner plate to cool.
We heat our 10-inch non-stick pan over medium heat with a dab of butter. We remove the manicotti batter from the fridge and stir briefly. When the pan is hot, we check by tossing in a drop of water and it sizzles, we add 1/4 cup of the batter. We tilt the pan and make a very thin “pancake” that is as large as the bottom of the pan. We cook for a little over a minute and then loosen with a heat-resistant rubber spatula. Using the spatula, we flip the “pancake”. The “pancake” is a golden color. We cook this other side briefly and remove it to a wax-paper lined dinner plate. We use a paper-towel to add another dab of butter to the pan and add another 1/4 cup of batter. When this “pancake” is flipped, we move the first “pancake” to another clean wax paper-lined dinner plate. We repeat this procedure, stacking the “pancakes” on top of each other on the second dinner plate. Since they are cooked on both sides, they will not stick together. These “pancakes”, or “crepes”, are a little tricky and sometimes the very tender dough tears. They all come together when baked, though! We have 10 manicotti wrappers to fill after a half-hour of standing by the stove. These manicotti wrappers can be prepared up to this point and refrigerated well wrapped for a day or frozen.
We are now ready to combine the cheeses. Over a piece of wax paper, we grate the mozzarella using our box grater. We put the shredded mozzarella into a 1-cup measuring cup. The small pieces of mozzarella that did not quite get shredded we put into a 1/4-cup measuring cup and reserve. We have a total of 1 1/4 cups of mozzarella (we also ate some!) We combine the 1-cup shredded mozzarella, Locatelli, and ricotta cheese in a large bowl. We add the cooled spinach-onion mixture, a few fresh gratings of nutmeg, and the fresh parsley. We also add some freshly ground black pepper, stir, and taste for seasoning (it’s delicious!)
We pre-heat the oven to 375 degrees and start heating our prepared tomato sauce. Next we coat the bottom of a 13 × 9 inch baking pan with some tomato sauce (it would have been easier if the pan was even larger than this). We place a couple of large spoonfuls of the spinach-cheese filling down the center of a manicotti wrapper. We place a few pieces of the reserved mozzarella on top of the filling and roll up. We don’t bother tucking in the sides, but you could roll it up like a burrito. We place it in the prepared baking dish and continue with the rest of the manicotti. We try and divide the filling equally among the 10 wrappers. We squeeze the filled manicotti into the baking pan and barely cover the top with some more tomato sauce. We place the pan, uncovered, into the oven and bake for 30 minutes.
We remove the bubbling pan from the oven and after a couple of minutes carefully serve the manicotti with additional hot tomato sauce.