For the fresh pasta:
Shape the flour into a gentle mound on your work surface or within a spacious vessel, fashioning a well at its heart. Crack the eggs into this central cradle and add a pristine pinch of salt. Begin to marry the ingredients with a fork, gradually drawing in the flour from the inner walls of the well. As the dough gains substance, commit to working it by hand, kneading with passionate energy for some 10 to 15 minutes, until you yield a smooth, supple, and elastic dough. Envelop this artisanal creation in cling film and allow it to rest at room temperature for at least 30 minutes. This pause is essential, allowing the gluten to relax so the dough may later surrender effortlessly to the rolling pin.

For the filling:
Lovingly wash the spinach and blanch them in boiling salted water for a fleeting few minutes, just until they wilt into submission. Drain and plunge them immediately into an ice-cold bath to arrest their cooking and preserve their vibrant, verdant hue. Squeeze them with utmost care to banish every drop of excess moisture, then finely mince them with a blade or pass them through a food mill. In a bowl, combine the finely minced, dry spinach with fresh cow's milk ricotta, which has been meticulously drained of its whey. Adorn the mixture with grated Parmigiano Reggiano PDO, a generous whisper of freshly grated nutmeg, and a pinch of salt. Blend these components with harmony until a uniform, compact filling is born. Taste your creation, elevating the salt if the palate demands.

For the shaping of the tortelli:
Retrieve your rested dough and portion off a small jewel of pasta, keeping the remainder draped in a damp cloth to prevent it from drying out. Flatten it gently with a rolling pin, then pass it through a pasta machine, starting at the widest setting and gradually refining it until you achieve a delicate sheet of sheer elegance, about 1-2 mm thick. Lacking a machine, let the rolling pin coax the dough until it is so fine it verges on translucency.
Divide the golden sheet lengthwise to create two majestic ribbons of dough. Using a fluted pastry wheel, carve out diamonds of approximately 10 cm on each side. Place a delicate dollop of the filling in the heart of each diamond. To bestow upon them the legendary silhouette of the Piacentine tortelli, fold the diamond in half, uniting two opposite points to form a triangle. Press the borders with intent to seal the precious filling within. Then, draw the two lateral tips toward the center, overlapping them gently, and pinch the upper peak to fashion the classic, braided "tail." Place the completed tortelli upon a lightly floured tray, ensuring they rest apart without kissing.

For the cooking and the finishing sauce:
Bring a grand pot of salted water to a rolling, lively boil. Meanwhile, in a shallow pan, allow the butter to melt softly over a gentle flame alongside fresh sage leaves, letting the butter become infused with their aromatic oils and the leaves turn crisp and translucent.
When the water is dancing, gently cradle the tortelli into the pot and cook them for about 3-4 minutes, or until they gracefully rise to the surface. Retrieve them with a slotted spoon and transfer them directly into the pan of melted sage butter. Toss the tortelli with gentle reverence for a single minute to envelop them in the golden elixir, then plate and serve immediately, crowned with a generous dusting of finely grated Parmigiano Reggiano PDO.