In a large pot, bring the mushroom broth to a boil, along with about a tablespoon of sea salt. Add pasta to boiling broth and simmer until al dente.
When the pasta is cooked, reserve about 1 cup of the cooking liquid and drain the rest. Set pasta aside in a separate bowl.
Return that same pot to medium-high heat and melt butter. Add mushrooms and garlic and sauté for about 5 to 10 minutes, allowing the mushrooms to caramelize until they're fragrant. Add the Sherry, ⅓ cup of the reserved mushroom broth, and cream and bring it all to a boil. Let simmer for about 10 minutes until the sauce has thickened to your desired consistency. Season it to taste with salt and pepper. If the sauce is thicker than you would like, add a bit more of the mushroom stock. Add the pasta back into the pot and toss everything until well combined. Sprinkle with Parmesan and chopped flat leaf parsley to serve.