Pat the duck legs dry with paper towels and season generously on both sides with salt and black pepper. Heat a large Dutch oven or heavy-bottomed pot over medium-high heat.

Place the duck legs skin-side down in the hot pot. Cook for 10-12 minutes until the skin is deep golden brown and much of the fat has rendered. Flip and cook for 2 more minutes, then transfer to a plate.

Carefully drain all but 2 tablespoons of the rendered duck fat from the pot. Lower the heat to medium, add the chopped onion, carrots, and celery, and sauté until softened and fragrant, about 8-10 minutes.

Stir in the minced garlic and ground cinnamon, cooking for 1 minute until highly fragrant. Pour in the red wine to deglaze the pot, scraping up any browned bits from the bottom, and let it simmer until the liquid is reduced by half.

Add the crushed tomatoes, broth, and whole rosemary sprigs to the pot, stirring well to combine. Return the duck legs and any resting juices to the pot, cover with a tight-fitting lid, and reduce the heat to low.

Simmer gently for 1.5 to 2 hours, or until the duck meat is exceptionally tender and easily falls off the bone. Remove the pot from the heat and carefully transfer the duck legs to a cutting board.

Once cool enough to handle, discard the duck skin, bones, and rosemary sprigs. Shred the meat using two forks and return the shredded duck to the sauce. Simmer uncovered for 10 minutes to thicken the ragu.

Meanwhile, bring a large pot of salted water to a boil and cook the pappardelle pasta according to package instructions until al dente. Drain the pasta, reserving 1/2 cup of the starchy pasta water.

Toss the cooked pasta directly into the rich duck ragu, adding a splash of the reserved pasta water if needed to help the sauce cling to the noodles. Serve hot in shallow bowls, generously garnished with grated Parmesan cheese.