Place the crawfish tails in a bowl and blend in some Creole seasoning. Set aside.
Chop the shallots and garlic very fine and set in separate prep bowls.
Finely chop the green onions and roughly chop the parsley and set aside in separate bowls.
Measure the butter, flour, creole seasonings, Worchestershire sauce and sherry. Pour the heavy cream in a measuring cup and let it come to room temperature.
To make the sauce
Melt the butter in a large saute pan over medium heat.
When butter is bubbling add the AP flour and stir constantly to make a light roux, about 3 minutes. See Notes.
Add the shallots to the roux and saute for about 3 minutes until softened, stirring constantly.
Add garlic, Creole seasonings and kosher salt and pepper, stir for about 2 minutes.
Increase heat to medium-high and add the parsley and crawfish tails.
Saute for about 3 minutes, stirring constantly.
Next add the Worcestershire sauce, sherry and green onions to the pan and stir constantly for about 1 minute.
Increase heat to high and add the heavy cream, stir or whisk to combine.
When the mixture begins to boil, reduce the heat to a low simmer.
Simmer for about 10 to 15 minutes, stirring and shaking the pan often until thickened slightly.
Notes
Notes You don’t want to make a brown roux for this, the lighter the better but you need to cook it long enough to cook the flour taste away. Normally a roux is equal parts fat and flour, but here we are using much more butter than flour. It will be smooth and still serve to thicken the sauce along with the heavy cream.If the sauce begins to separate, simply whisk the warm sauce until it's back together.You can substitute any dry white wine or this or even a light rum for the sherry. Of course, you could leave it out altogether.This sauce is great spooned over fried or broiled fish, stuffed peppers and even on Pasta. There really is no end to how you will use this sauce.