Cream of mushroom soup is typically a condensed soup that is very thick in texture and meant to be used as an ingredient in other dishes. Mushroom bisque is an elevated mushroom soup with a small amount of cream that is not nearly as thick and is meant to be served as a soup on its own. Bisque is a misnomer here, since bisque originally referred to creamy shellfish soups, but is now used to indicate an elegant soup that is finished with cream.