Bring a large pot of generously-salted (very important as this dish is so simple) water to a boil and cook pasta to just under al dente according to package instructions. If the package says 9 minutes, take out around 7. Reserve 1 cup of starchy pasta water before straining.
In a dry, heavy-bottom skillet set over medium-high heat, brown mushrooms in batches until golden and crisp. I browned each variety of mushroom on its own as they may have different moisture levels. It should take about 6-7 minutes per batch to get them nice and golden - don't rush this part. It's the big flavour maker!
Once all your mushrooms have been browned, remove everything from the pan. Add the butter and olive oil to pan and let it get shimmering and hot. Add the garlic and let it cook until fragrant, 1 minute. Add the mushrooms, parsley and red pepper flakes and sauté until everything is combined, 1-2 minutes. Remove from heat.
Strain pasta (don't forget to reserve 1 cup starchy water), and add back to large pot. Scoop the mushroom mixture into the pasta, making sure to really scrape all the good bits from the pan, with the Parmesan cheese and 1/4 cup of starch water and toss. If it's too dry, add more water a little at a time until you've got a nice, loose mushroom sauce coating all the noodles. Taste for seasoning and add salt if needed.
Garnish each serving with pine nuts, extra cheese, parsley and fresh ground pepper.