In a large skillet over medium heat, drizzle in 2 tablespoons of extra-virgin olive oil. Allow it to warm for about 1-2 minutes until shimmering, then add 1 finely sliced shallot. Sauté the shallot until it softens and becomes translucent, about 3-4 minutes.

Next, stir in 8 ounces of sliced portobello mushrooms along with a pinch of kosher salt. Cook for roughly 5-7 minutes, stirring occasionally, until the mushrooms are tender.

While the mushrooms are cooking, bring a large pot of salted water to a rolling boil. Add 12 ounces of pappardelle pasta and cook according to package instructions, usually around 8-10 minutes.

With the mushrooms tender, mix in 2 minced garlic cloves, 1 tablespoon of fresh rosemary leaves, and a pinch of crushed red pepper to taste. Stir in 2 tablespoons of tomato paste and 1 tablespoon of balsamic vinegar, allowing to simmer for about 2-3 minutes.

Add the drained pappardelle into the skillet with the mushroom sauce. Toss gently for about 1-2 minutes, ensuring the pasta is fully coated. If the mixture appears dry, gradually pour in some reserved pasta water.

To finish, stir in 2 tablespoons of unsalted butter until melted and glossy. Serve warm, garnished with freshly shaved Parmigiano Reggiano.