Heat the butter in a large skillet over medium heat. Sauté the green onions and shallots until they're limp.
Add the wine and bring it to a boil. Reduce until most of the liquid is gone. Add the cream, saffron, salt, pepper, cayenne and ginger, and bring to a light boil. (Also add tarragon at this point if using dried.)
Add scallops and shrimp. Cook for four minutes, then add oysters and fresh tarragon. Cook until edges of oysters are curly, then add the crabmeat. Throughout the process, agitate pan to slosh the sauce over the seafoods.
Taste the sauce and add salt if necessary. You can also spice it up with a bit of Tabasco or crushed red pepper. Remove from the heat.
Add the cooked pasta to the pan and toss with the sauce ingredients to coat the pasta and distribute the seafoods.