You can refrigerate leftover Oyster Soup for about 3 to 4 days as long as you use an airtight container. Let the soup cool off before refrigerating. Reheat in a saucepan over medium heat until completely warmed through. If the milk, cream and butter start to separate, stir or whisk vigorously until it is repaired. I don’t recommend freezing leftover Oyster Soup, but it can be done. Actually, I’ve never really had enough leftover to worry about it. The problem with freezing Oyster Soup is that the solids in the butter/milk/cream may separate from the liquid and the oysters may lose a little of their texture and flavor. But like I said, it can be done with no problem and the soup should maintain good quality for up to 3 months if stored in an airtight container. Defrost the soup in the refrigerator, then warm slowly in a saucepan. If there is a lot of separation, pull the oysters out of the soup with a slotted spoon. Vigorously whisk the soup while it is heating up, then put the oysters back in and let them warm through. If you think it needs it, you can whisk in a small amount of warm milk.