Bring a large pot of salted water to a rolling boil over high heat. Add the rigatoni pasta and cook until al dente, about 10-12 minutes. Reserve ½ cup of pasta water before draining.

In a large, deep skillet, melt the salty butter over medium heat. Swirl the pan for about 3-4 minutes until it turns golden brown and develops a nutty aroma.

Add the sliced cremini or baby bella mushrooms to the skillet and cook for about 5 minutes, until they are tender and browned.

Stir in the chopped garlic and dried thyme, and cook for an additional 2 minutes. Season with kosher salt and black pepper to taste.

Add the drained rigatoni to the skillet with the mushroom mixture. Pour in the reserved pasta water and mix everything together, adding half of the Parmesan cheese.

Incorporate the remaining Parmesan cheese until melted and the sauce is smooth. Add more reserved pasta water if the sauce is too thick.

Serve hot, garnished with chopped fresh parsley, and offer crushed red pepper flakes and more Parmesan on the side.