Cook the pasta to al dante in boiling salted water according to box instructions. Keep 1 cup of the pasta cooking water then drain the pasta.
In a large skillet, heat the olive and butter over medium-high heat, add the shallots and garlic and cook, tossing regularly for 2 to 3 minutes (manage the heat so that the garlic does not burn).
Add all the mushrooms and toss them around in the pan for a couple of minutes, adding another drizzle of extra virgin olive oil. Season with a good pinch of kosher salt, black pepper and the rosemary. Cook the mushrooms for about 7 to 10 minutes, tossing occasionally, until they turn color and release their juices.
Add the tomato paste, wine and about ½ to 3/4 cup of the pasta cooking water. Cook over medium heat for about 4 to 5 minutes (this becomes your mushroom pasta sauce).
Add the cooked pasta to the mushroom sauce. Toss to combine. If needed add a little bit more of the pasta cooking water.
Stir in Parmesan cheese and finish with a sprinkle of parsley, walnuts and red pepper flakes. Serve immediately!
