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, 3 turns of the pan. 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. If using raw seafood, season with lemon zest, salt, and pepper. Raise the heat a bit then add the seasoned seafood and heat through or cook until just about firm and opaque, a couple of minutes. If using cooked seafood, season the seafood when you add it to skillet with lemon zest, salt and pepper.
Stir in heavy cream and toss hot pasta with sauce and chives and/or parsley, adjust seasoning and serve.