Ingredients

• 3 tablespoons extra-virgin olive oil
• 2 medium shallots, halved lengthwise and thinly sliced
• Kosher salt
• 3 portobello mushroom caps (10–12 ounces), sliced into 1-inch pieces
• 8 ounces pappardelle pasta, fresh or dried
• 1 garlic clove, finely sliced
• 2 teaspoons fresh rosemary leaves, finely chopped
• ½ teaspoon red pepper flakes
• 2 tablespoons tomato paste
• 1 teaspoon balsamic vinegar
• 2 tablespoons unsalted butter
• Parmigiano Reggiano or Parmesan cheese, for shaving
• Pasta water, reserved

Steps

1. Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Reserve ¾ cup pasta water and drain.
2. Meanwhile, heat olive oil, shallots, and a pinch of salt in a large skillet over medium heat. Cook, stirring frequently, until shallots are softened but not browned, about 5 minutes.
3. Add mushroom pieces to the skillet. Cook for a few minutes until they take on some color, then stir in ½ teaspoon salt. Continue cooking until mushrooms are tender and their liquid evaporates, about 8–10 minutes.
4. Add garlic, rosemary, red pepper flakes, tomato paste, vinegar, and butter. Stir in ½ cup pasta water and cook over medium heat until the sauce becomes cohesive and saucy, about 2 minutes.
5. Add cooked pasta to the skillet and toss gently with tongs to coat. Add more pasta water if the sauce is too dry. Taste and adjust seasoning.
6. Shave curls of Parmigiano over the pasta with a vegetable peeler and serve.