Oyster and Artichoke Soup

1/2 cup butter
2 bunches green onions, chopped
3 ribs celery, chopped
3 cloves garlic, pressed
2 (14 oz) cans artichoke hearts, washed, drained, and quartered
3 tablespoons flour
1- 1 1/2 quarts chicken stock
Cayenne to taste
1 teaspoon salt
1 tablespoon Worcestershire sauce
1/4 teaspoon thyme
1 quart oysters, drained and chopped (reserve liquor)
1/3 cup sherry
1 cup half-and-half cream
1 cup milk

In a heavy 4-quart pot melt the butter over medium heat.  Add the green 
onion, celery, and garlic and saute' until soft.  Add the artichokes.  
Sprinkle the mixture with the flour and stir to coat the vegetables 
well, but do not let the flour brown.  Gradually add the stock, stirring 
constantly.  Add the cayenne, salt, Worcestershire sauce, and thyme.  
Simmer the mixture, covered, for 1 hour.  Add the oysters, oyster 
liquor, and sherry and simmer for 10 minutes.  Do not allow the soup to 
boil.  Stir in the cream and milk.  Cool and refrigerate for at least 8 
hours.  Before serving, heat the soup slowly over low heat.  Serves 8 
bowls or 16 cups.