Heat 1 tablespoon of the olive oil in a large cast iron skillet over medium-high heat. Add half the mushrooms, 1/4 teaspoon of the salt, and several grinds of pepper and toss. Cook, stirring only occasionally, for 5 to 8 minutes, or until soft and browned. Remove from the skillet and set aside. Add the remaining 1 tablespoon olive oil to the skillet and repeat the cooking process with the remaining mushrooms.

Meanwhile, bring a large pot of salted water to a boil. Prepare the pasta according to the package directions, cooking until al dente. Reserve 1 cup of the pasta cooking water before draining. Drain the pasta and toss it with a drizzle of olive oil to prevent sticking.

Allow the pasta pot to cool slightly and return it to the stove. Add the butter and heat over medium heat until melted, then add the shallots and the remaining 1/4 teaspoon salt and cook, stirring, for 3 to 5 minutes, or until translucent. Stir in the rosemary and garlic. Add the wine and Dijon mustard and let the wine cook down for 30 seconds.

Add the pasta, cheese, and 1/4 cup of the pasta water and toss, adding more pasta water as needed to lightly coat the pasta. Stir in the lemon juice, then fold in the mushrooms. Sprinkle with parsley and season to taste. Serve with more grated cheese.