Preheat the oven to 400 degrees F.

Place the puff pastry shells on an ungreased baking sheet. Bake until golden brown, 15 to 20 minutes. Remove the tops, pull out any uncooked pastry and discard. Return the shells and tops to the oven and bake for 2 minutes. Remove and let rest.

In a large skillet or saute pan, melt 2 tablespoons of butter over medium heat. Add the shallots and garlic, and cook, stirring, until soft, 2 minutes. Add the oysters and their liquid, crawfish tails, scallops and Essence and cook, stirring, until the oysters curl and the scallops turn opaque, 3 to 4 minutes. Remove the seafood with a slotted spoon to a bowl. Add the wine and cognac and bring to a boil. Cook until reduced by 1/2. Add the fish stock, salt, and cayenne, and cook until reduced by 1/2. Reduce the heat to medium-low. Stir in the tomatoes and cook for 1 minute. Whisk in the remaining 6 tablespoons of butter 1 tablespoon at a time, adding the next piece before the previous one is completely incorporated, being careful not to let the sauce get too hot and break. Add the green onions, parsley, and tarragon and stir. Return the seafood and any accumulated juices to the pan and cook, stirring until heated through. Remove from the heat and adjust the seasoning, to taste.

Place 1 puff pastry shell on each of 6 medium plates. Divide the seafood sauce among the pastries and arrange the pastry lid on top of each. Garnish each plate with 2 chives and sprinkle chopped parsley around the sides. Serve.