Melt 1/2 stick (4 tablespoons) of the butter in a skillet over medium-high heat. Add the flour and cook, stirring constantly, for 3 to 4 minutes to make a blond roux, the color of sandpaper.
Add the onions and cook for 2 minutes. Add the milk, oyster liquor, salt, cayenne, and black pepper and bring to a gentle boil. Stir constantly for 3 to 4 minutes, or until the mixture thickens slightly. Add the parsley, green onions, garlic, and oysters. Bring to a gentle boil and cook until the edges of the oysters curl, 3 to 4 minutes.
Cut the remaining 2 tablespoons of butter into chips and add to the stew.
Remove from the heat and serve immediately.
Yield: 4 main-course servings