Bring a large pot of salted water to a rolling boil. Use about 4 liters of water for 400 g fresh pasta and salt it generously (about 1–1.5% salinity; ~40 g salt). Salting the water is your first chance to season the pasta itself so the noodles have flavor through and through.

While the water heats, prep mise en place: slice mushrooms, finely dice the onion, mince garlic, chop parsley, and weigh the pork. Having everything ready keeps the cooking rhythm steady so the pork browns properly and the mushrooms caramelize without overcooking.

Heat a wide, heavy skillet or sauté pan over medium-high heat. When hot, add 2 tablespoons olive oil. Swirl to coat. A hot pan and a thin layer of oil help dry-sear the mushrooms so they color and concentrate their flavor instead of steaming.

Add the sliced mushrooms in a single layer (work in two batches if the pan is crowded). Let them sit undisturbed for 1–2 minutes to develop color, then stir and cook until nicely browned (about 4–6 minutes total). Season lightly with salt to draw out moisture. Browning (Maillard reaction) gives mushrooms rich, meaty umami that elevates the ragù.

Transfer the browned mushrooms to a bowl and set aside. In the same pan over medium heat, add the remaining 2 tablespoons olive oil. Add the diced onion and cook, stirring occasionally, until translucent and starting to caramelize, about 6–8 minutes. Sweating the onion builds sweet, savory depth in the sauce.

Add the minced garlic and red pepper flakes to the onion and toast for 30–45 seconds until fragrant. Toasting the aromatics in fat blooms their flavors and releases volatile oils — don’t let the garlic burn, or it will become bitter.

Increase heat to medium-high and add the ground pork (or sausage meat). Use a wooden spoon to break it into small pieces. Spread it out across the pan so it contacts the surface — this maximizes browning. Cook, stirring occasionally, until the pork is well browned and no longer pink, about 6–8 minutes. Browning creates concentrated savory flavors and texture in the ragù.

Season the browned pork with salt, several grinds of black pepper, and taste for heat — add an extra pinch of red pepper flakes now if you want it spicier. Then pour in the tomato passata and bring to a gentle simmer. Use passata for a bright, smooth tomato body that clings to wide noodles.

Return the browned mushrooms to the pan, stir to combine, and simmer the ragù over medium-low heat for 8–12 minutes, uncovered, until slightly reduced and glossy. Simmering melds the pork and mushroom flavors into the tomato and allows some water to evaporate so the sauce coats pasta rather than pooling.

While the ragù simmers, cook the fresh pappardelle in the boiling water. Fresh pasta cooks quickly — start checking at 2 minutes and expect 3–4 minutes total depending on thickness. Cook to just shy of al dente (a minute firmer than you want) because it will finish cooking in the sauce and absorb flavor.

Reserve 1 cup (240 ml) of pasta cooking water, then drain the pasta. The starchy cooking water is a seasoning and binder — add it a little at a time to adjust sauce consistency and help it cling to the noodles.

Raise the heat under the ragù to medium. Add the drained pappardelle directly to the pan and toss gently with a pair of tongs. Add a splash (2–4 tablespoons) of the reserved pasta water and toss until the sauce emulsifies and coats the noodles; add more as needed for silkiness. This technique (finishing pasta in the sauce) creates a cohesive, restaurant-quality coating.

Remove from heat. Stir in chopped parsley and, if using, finely grate 30–40 g Parmesan into the pan for a glossy, savory finish (reserve a little for serving). Taste and adjust salt, pepper, and red pepper flakes.

Divide the pasta among warmed bowls, finish with the remaining Parmesan, an extra drizzle of olive oil, and an optional pinch of chopped parsley and red pepper flakes. Serve immediately so the noodles remain glossy and the ragù warm.