Melt butter in a skillet set over medium high heat. Add the green onion and parsley and sauté until wilted, about 4 minutes. Add the crawfish tails and garlic and cook until garlic is slightly fragrant, about 2 minutes. Add the cheese and the cream and cook until cheese is melted, about 5 minutes. Add the cayenne, salt, pepper and vermouth. Stir, reduce heat to medium-low, cover and cook until flavors marry and sauce is slightly thickened, about 15 minutes. Spoon heaping teaspoons of the sauce into the warm vol au vents. Serve at once.

Notes: 1.Puff pastry vol au vents are available fresh from the bakery or from the frozen bread section at most groceries. Pepperidge Farm is a popular frozen brand.2.This dish works well as a filling for vol au vents(puff pastry shells), tossed with pasta, or served as a dip (use less vermouth and cream and a bit more cheese).