Creamy and rich describes a bisque, but beyond these characteristics it may be hard to determine what separates it from regular soup. A classic French concoction, bisque technically designates a soup made from a shellfish broth, but you can now find versions that are made with fresh produce and don't contain any crustaceans whatsoever. If you order a bisque or plan to serve one, understand exactly what it is.
Original recipes for bisque usually used shellfish of some sort by grinding the shells or the entire shellfish into a paste to thicken the soup; at least a fish or shellfish stock featured prominently. Shrimp bisque, oyster bisque and crab bisque are traditional interpretations. The addition of wine or another spirit, such as cognac, and heavy cream are other hallmarks of a bisque.
Now, a bisque may be defined as a creamy soup that is thickened with pureed rice. It's separate from a chowder, for example, which is usually chunky and doesn't always contain alcohol. Creaminess defines the soup, such as in corn bisque or tomato bisque. In produce versions, expect the addition of an ingredient that adds a silky texture, such as pureed potatoes, rice, dairy or coconut milk. Liquor is optional and not always included in vegetable versions.
No Flour Thickening
Bisque differs from cream soups and chowders that are thickened with flour. Cream soup usually features a bechamel, a cooked combination of butter and flour thickened with milk; chowders simply use flour in a slurry to add thickness.