Bring a large pot of salted water to a boil. Add the dried pasta and cook according to the package instructions until al dente. Make sure to reserve 1 cup of the pasta cooking water before draining. Drain the pasta and set aside.

In a large skillet over medium-high heat, heat 1/3 cup of extra-virgin olive oil and 1 tablespoon of unsalted butter. Add the minced shallots and garlic, and cook, stirring regularly, for 2 to 3 minutes until fragrant and slightly softened. Adjust the heat as needed to prevent the garlic from burning. I find that stirring consistently helps release the best aroma from the garlic!

Add all the sliced and chopped mushrooms to the skillet with the shallots and garlic. Toss the mushrooms for a couple of minutes, adding another drizzle of olive oil if the pan seems dry. Season with a generous pinch of kosher salt, black pepper, and the dried rosemary. Continue to cook for 7 to 10 minutes, tossing occasionally, until the mushrooms change color and release their juices.

Add the tomato paste and merlot wine to the skillet with the mushrooms. Pour in about 1/2 to 3/4 cup of the reserved pasta cooking water. Stir well and cook over medium heat for 4 to 5 minutes. The liquid will reduce slightly, creating a flavorful mushroom pasta sauce.

Add the cooked pasta (from Step 1) to the skillet with the mushroom sauce. Toss to coat the pasta thoroughly. If the mixture seems dry, add a bit more of the reserved pasta cooking water until the desired consistency is reached.

Remove the skillet from the heat. Stir in the grated Parmesan cheese. Finish the dish with a generous sprinkle of chopped parsley and walnuts. If you like a touch of heat, sprinkle with red pepper flakes. Serve immediately! For a bold flavor, I like to add a little extra Parmesan at the table.