Cream soups are a frugal cook's best friend, quickly turning excess broccoli or any other vegetable into a hearty first course or a light lunch. Typically the goal is to create a soup that has approximately the same consistency as heavy cream, but sometimes a thicker soup is appropriate. You might want a heartier cream of broccoli for a warming mid-winter lunch, or to use as the sauce in a casserole. There are a few easy ways to do this, regardless of how you prepare your soup.
Broccoli Soup in a Nutshell
Most recipes for cream of broccoli soup broadly fall into two categories. Fast, simple modern recipes call for the broccoli to be simmered in a small amount of broth, with flavoring ingredients such as onions or shallots. Then they're pureed, and the soup is finished with a small quantity of heavy cream. Classic, restaurant-style cream of broccoli soup begins the same way, but instead of heavy cream, it's finished with a thickened, cream-based sauce. The classic version is the thicker of the two, but either style can be tweaked to make it heartier.
Up the Broccoli
A few techniques work for both styles of soup. One option is to increase the amount of broccoli you use. The pureed vegetable gives your soup extra body, fiber and nutrition, as well as a fresh green color. Don't overlook the broccoli stems. If you peel away the tough skin, the stems provide a large quantity of extra vegetable to cook and puree. A closely related option is to reduce the quantity of water or broth you use to simmer the broccoli. That yields a smaller batch of soup, but the result will be thicker.
Ramp Up the Roux
Classic cream of broccoli soup is thickened with a roux, a mixture of equal parts butter and flour that's cooked to a thick paste. Whisk a hot, seasoned mixture of milk and cream into the roux, then cook it for approximately 20 to 30 minutes, or until the mixture has thickened. Making this type of soup thicker is a simple matter of using more roux. Typical recipes use 2 to 3 tablespoons each of flour and butter to thicken a pint of cream. You can double that quantity for an extra-thick sauce.
Tweaking Quick Soups
Aside from tweaking the ratio of broccoli to broth, the most reliable way of thickening quick broccoli soups is to use a starch-based thickener. The most opportune time to do that is after you've pureed the broccoli, but before you add the cream. You can use roux to simulate the silky smoothness of a classic-style soup, simmering it until it's very thick and then adding cream until you reach the consistency you want. Alternatively, use a quick thickener such as cornstarch or quick-mixing flour or potato starch. Stir it into cold water or broth to make a slurry, then whisk that into your pureed soup base. As it simmers, the soup will thicken dramatically, then you can thin it with heavy cream until you reach the right consistency.