Bring a large pot of generously salted water to a rolling boil. Add the rigatoni and cook until 1 to 2 minutes shy of al dente according to package directions (about 10 to 11 minutes). Before draining, carefully scoop out and reserve 1/2 cup of the cloudy, starchy pasta cooking water. Drain pasta and set aside.

While the pasta boils, heat 1 tablespoon of olive oil in a large deep skillet or Dutch oven over medium heat. Add the fresh sage leaves in a single layer and fry for 1 to 2 minutes until dark green and crispy. Use a slotted spoon to transfer fried sage leaves to a paper towel-lined plate to drain (leave fragrant herb oil in the skillet).

Add the crumbled Italian sausage to the hot skillet. Cook for 6 to 8 minutes, breaking it into bite-sized caramelized crumbles with a wooden spoon, until golden brown and cooked through. Transfer browned sausage to a plate, leaving about 1 tablespoon of rendered drippings in the pan.

Melt 2 tablespoons of butter in the skillet over medium-low heat. Add the minced shallot and garlic. Saute for 2 minutes until translucent and aromatic, scraping up any delicious browned sausage bits from the bottom.

Whisk in the pure pumpkin puree, chicken broth, heavy cream, freshly grated nutmeg, red pepper flakes, sea salt, and black pepper. Bring to a gentle simmer and cook uncovered for 4 to 5 minutes, whisking frequently, until the sauce turns smooth, glossy, and slightly reduced.

Lower heat to low. Stir in the freshly grated Parmigiano-Reggiano cheese until melted into the sauce. Add the drained rigatoni pasta and browned sausage crumbles back into the skillet. Toss vigorously for 1 to 2 minutes so the velvety pumpkin cream coats every ridge and fills the pasta tubes, splashing in reserved pasta water as needed to achieve a luxurious glossy coating.

Divide pasta into warm shallow bowls. Garnish with the crispy fried sage leaves, extra shaved parmesan cheese curls, and a turn of freshly cracked black pepper. Serve immediately and enjoy!