1Soak porcini in boiling water for 10 minutes, reserve 5 Tbsp soaking liquid, and then finely chop mushrooms.
2Bring a pot of salted water to a boil and boil pasta until al dente, reserving 1 3/4 cups pasta water.
3In a cold large sauté pan, gently cook olive oil, garlic, red pepper flakes, parsley, and a pinch of salt over medium-low until soft.
4Increase heat, add mushrooms, tomato paste, and 50 cracks of black pepper, and cook.
5Return pan to medium-high, add 1 1/2 cups pasta water plus porcini liquid, simmer, then stir in Parmesan until melted, followed by cream and drained pasta.
6Toss until emulsified, adding more pasta water if needed, and finish with olive oil, Parmesan, and parsley.