In a large saucepan boil water for the pasta. When water begins to boil add salt liberally, let water return to a boil and cook pasta to al dente. Drain.
Heat a large skillet over medium heat with olive oil. Add mushrooms, shallots and garlic, red pepper flakes and saute 5 minutes.
Deglaze the pan with sherry, stir in stock and tomatoes and bring to a bubble.
Chop seafood into good-sized pieces. Season with lemon zest, salt and pepper. If using cooked seafood, add to sauce and proceed to next step. If using raw seafood, add to pot, cook a few minutes until it is opaque, then proceed to next step.
Stir in heavy cream and toss hot pasta with sauce and chives and/or parsley, adjust seasoning and serve.