In a large skillet, heat 2 tablespoons of olive oil over moderate heat. Add 1 finely chopped shallot and a pinch of salt. Sauté for about 3–4 minutes until tender and translucent.

Add 8 ounces of thinly sliced portobello mushrooms to the skillet. Cook for about 5–7 minutes until golden brown and moisture evaporates.

In a separate pot, bring water to a boil and add kosher salt. Cook 12 ounces of pappardelle pasta according to package instructions, around 3–4 minutes till al dente. Reserve 1 cup of pasta water.

To the mushroom skillet, add 2 minced garlic cloves, 1 tablespoon of tomato paste, 1 tablespoon of balsamic vinegar, and 1 teaspoon of fresh rosemary. Cook for an additional 2 minutes.

Pour in a splash of reserved pasta water and 2 tablespoons of butter, stirring until glossy. Toss in the drained pappardelle, adjusting with more pasta water for consistency.

Plate the dish while hot and grate Parmigiano Reggiano over the top. Serve immediately.