A good bisque reflects the flavor of the main ingredient. If you have added cream to round out and mellow the soup, it should not mask the main flavor. All bisques are slightly coarse or grainy, with a consistency similar to heavy cream. A crustacean bisque is pale pink or red in color; a shellfish bisque ivory; and a vegetable bisque a paler shade of the main vegetable.
1. Prepare the shells
Rinse the shells well and chop larger shells, such as crab or lobster. Drain and dry them well. Traditional bisques get their color and flavor from shrimp, lobster, crab, or crayfish shells. Use one type of crustacean or a combination. Brown the shells in the cooking fat, stirring frequently, until they turn a bright pink or red and remove them from the pan.
2. Add the aromatic ingredients
Add the mirepoix to the pan and cook it over medium heat for 20 to 30 minutes, or until the vegetables are tender and the onions are light brown. Tomato paste is often added at this point and allowed to cook until it has a sweet aroma and a deep rust color. Add spices such as paprika to the shells and other aromatics to cook in the fat.
3. Thicken the soup
Some bisque recipes indicate the addition of flour to prepare a roux as part of the soup-making process. If necessary, add a bit more oil or butter to the shells, then stir in the flour and cook the result roux, stirring constantly, for 4 to 5 minutes. A good quality stock or broth is as important to the flavor of a bisque as the shells are. Bring the broth to a simmer while cooking the aromatic vegetables to make cooking more efficient. Also, a more traditional rice-thickener can be used instead of flour that has been cooked into a roux. Once the soup is simmering, add the wine (if called for) and any additional herbs or aromatics, such as a spice sachet or bouquet garni.
4. Purée the soup
Taste the soup and make modifications to the seasoning or consistency during cooking. Add more liquid, if necessary, to maintain a good balance between the liquid and solids as the soup cooks. Stir frequently and monitor the heat. A bisque, like any other soup with starchy ingredients, can scorch quickly if left unattended for even a few minutes. A bisque takes about 45 minutes to 1 hour to cook properly. At that point, all ingredients (except, obviously, the shells) should be relatively tender, so they will purée easily. Skim the bisque throughout.
Remove and discard the sachet or bouquet garni before puréeing the bisque. Use a blender (immersion or countertop) to purée it to a fairly smooth and even consistency. Pulverizing the shells and puréeing the aromatic vegetables helps to release more flavor into the soup. If time allows, return the puréed bisque to a simmer for several minutes and make any appropriate adjustments to the soup’s seasoning or consistency before straining.
5. Strain the soup
The soup can be strained through a fine mesh sieve. Or, for a fine, delicate texture, use rinsed cheesecloth to strain a shellfish bisque. Cheesecloth removes all traces of the shell. This is a two-person task.
First, set a sieve or colander in a clean pot. Drape the rinsed cheesecloth in the sieve or colander and pour the bisque through it. Most of the bisque will pass through the cheesecloth. Each person holds two corners of the cheesecloth and lifts the corners up in an alternating sequence (known as the milking method). When only solids remain in the cheesecloth, each person gathers his or her corners together and twists in opposite directions to finish straining the bisque (known as the wringing method). The bisque is ready to finish now, or it may be rapidly cooled and refrigerated for later service.
6. Finish the soup
Finish the bisque and add any garnish ingredients. Return the bisque to medium heat and bring it to a simmer. Taste the soup and make any seasoning adjustments. Separately, bring the cream to a simmer and add it gradually to the bisque. There should be enough cream to enrich the soup and add a smooth flavor and mouthfeel, but not so much that the cream masks the main ingredient.
