Drain the oysters, reserving the liquor. In a large, heavy pot or Dutch oven, cook the white parts of the green onions in the butter until they are very soft. Add the chicken broth and oyster liquor. Simmer for 30 minutes. Add the half-and-half or heavy cream and continue to simmer for another 30 minutes. The soup should be the consistency of heavy cream. Season to taste with salt and peppers. At a low simmer, drop in the oysters and cook just until the edges curl, 1 to 2 minutes. Serve garnished with chopped green onions.
Makes 4 servings