HOW TO MAKE SOUP

Making soup is one of the easiest and most rewarding kitchen tasks. The basic ingredients—stock, onions, carrots, potatoes, and herbs—are almost always on hand. The technique is simple. Most recipes begin with the sautéing of aromatic vegetables to build flavor. Liquid is then added along with the distinguishing ingredients—tomatoes for cream of tomato soup or lentils for a lentil soup—and everything is simmered until tender.

Although this process sounds simple (and it is), there are a number of issues that require some special attention.

STOCK

Perhaps the most important issue that faces the cook when making soup is the choice of liquid. Without a doubt, homemade stock (usually chicken stock) is the best option. It has a rich flavor that complements not only chicken but also vegetables, grains, and beans. Certain recipes are best made with something other than chicken stock (as you will see in this book), but if you keep just one homemade stock on hand, make it chicken stock.

We find that beef stock has it uses, especially in a beef soup. It is also delicious (but not essential) in French onion soup. We understand the appeal of vegetable stock for vegetarians, but, given a choice, we always opt for chicken stock, even in a vegetable soup. Of course, if you don't eat meat, you can use vegetable stock, either homemade or store-bought, in any vegetable or bean soup recipe in this book and achieve fine results. In many cases, you could even use water. Soups made with water or vegetable stock will, however, taste less complex.

Our chicken stock takes just an hour to make and is worth the minimal effort. Unfortunately, even the most diligent cook may not always have the time to make homemade stock. Canned broths make good soups, especially if you follow some simple guidelines.

Avoid canned beef broths at all cost. We tested 11 leading brands of canned beef broth and beef bouillon cubes and could not find one that we liked. None really tasted like beef, and most had strong off flavors. Government regulations require makers of beef broth to use only 1 part protein to 135 parts moisture in their product. That translates into less than 1 ounce of meat to flavor 1 gallon of water. (In contrast, our homemade beef stock uses 6 pounds of meat and bones to flavor 2 quarts of water.) Most manufacturers use salt, monosodium glutamate (MSG), and yeast-based hydrolyzed soy protein to give their watery concoctions some flavor and mouthfeel. None of these cheap tricks works.

By comparison, canned chicken broth is far superior. In our tasting of 10 leading brands, we found several that actually tasted like chicken. However, many brands are overly salty, which may explain why low-sodium broths made by Campbell's and Swanson (both brands are owned by the same company) topped our ratings.

Most commercial brands of stock come in cans that measure just under two cups. (Aseptic paper containers generally hold a liter, or just more than four cups.) If using the smaller cans, just add a little water to stretch the broth as needed in recipes. For instance, if a recipe calls for four cups of broth, use two cans of broth plus a few extra ounces of water to make four cups.

STORING AND REHEATING SOUP

One of the beauties of soup is the fact that it holds so well. Make a pot on Sunday and you can enjoy soup several times during the week. Unless otherwise specified, all the soups in this book can be refrigerated for several days or frozen for several months. Store soup in an airtight container. When ready to serve, reheat only as much soup as you need at that time. You can reheat soup in the microwave or in a covered saucepan set over medium-low heat. Because the microwave heats unevenly, this method is best for single servings. Just heat the soup right in the serving bowl or mug. Larger quantities of soup are best reheated on the stovetop.

You may find that a soup has thickened in the refrigerator or freezer. (As soup cools, liquid evaporates in the form of steam.) Simply thin out the soup with a little water to achieve the proper texture.

While most soups can be cooled, then reheated without harm, some will suffer, especially in terms of texture. Soups with rice and pasta are best eaten immediately. When refrigerated, rice and pasta become mushy and bloated as they absorb the liquid in the soup. If you plan on having leftovers, cool the soup before adding the rice or pasta, which is often the last step in most recipes. Add a portion of the rice or pasta to the soup you plan on eating immediately, then add the rest when you reheat the remaining soup.

Soups with seafood also fail to hold up well. For instance, clams will become tough if overcooked by reheating. These soups are best served as soon as they are done.

Finally, pureed soups made from green vegetables will look their best if served immediately upon completion of the recipe. Reheating breaks down the chlorophyll in some green vegetables (asparagus is especially prone to this problem). A soup that is bright green can turn drab army green if stored for several hours and then reheated. Of course, these soups will still taste delicious, but their visual appeal will be greatly diminished.

EQUIPMENT

Soupmaking requires just a few pieces of equipment. At the most basic level, all you need is a pot and spoon. Here are our recommendations for all the equipment used in this book.

SOUP KETTLE/DUTCH OVEN

Most soups can be prepared in a small stockpot (also called a soup kettle) or Dutch oven. These pots work best because they are generally quite large (at least seven quarts) and have two handles, which makes lifting much easier. Dutch ovens are twice as wide as they are high. For stockpots, the opposite is true—they are generally twice as high as they are wide.

Because of their different shapes, we find it slightly easier to sauté in a Dutch oven. There's more surface area, and the vegetables are easier to stir in a shallower pot. This greater surface area also causes soups simmered uncovered to reduce and condense more than they would in a stockpot.

Another consideration when choosing a pot for soupmaking is cost. Most Dutch ovens are designed for making stews and braises and have thick, heavy bottoms that will ensure good results when browning meat. Consequently, most good Dutch ovens cost about $150. We found that cheaper Dutch ovens cause pan drippings to burn. For soupmaking, though, you can get away with a cheaper stockpot because it is used mostly for simmering liquids. In most soup recipes, a cheap aluminum stock pot will deliver fine results. As an added advantage, these pots are lightweight and easy to carry from the stovetop to the counter or sink.

BLENDER

The texture of a pureed soup should be smooth and creamy. With this in mind, we tried pureeing these soups in a food mill, a food processor, and a regular countertop blender, as well as with a handheld immersion blender.

Forget using the food mill for this purpose. We tried all three blades (coarse, medium, and fine), and, in each case, the liquid ran right through the blade as we churned and churned only to produce baby food of varying textures. Once separated, the liquid and pureed solids could not be combined with a whisk.

The food processor does a decent job of pureeing, but some small bits of vegetables can be trapped under the blade and remain unchopped. Even more troubling is the tendency of a food processor to leak hot liquid. Fill the workbowl more than halfway and you are likely to see liquid running down the side of the food processor base. Even small quantities of soup must be pureed in batches, and that's a hassle.

The immersion blender has more appeal since this tool can be brought directly to the pot and there is no ladling of hot ingredients. However, we found that this kind of blender also leaves some chunks behind. If you don't mind a few lumps, use an immersion blender.

For perfectly smooth pureed soups, use a regular blender. As long as a little headroom is left at the top of the blender, there is never any leaking. Also, the blender blade does an excellent job with soups because it pulls ingredients down from the top of the container. No stray bits go untouched by the blade.

Depending on the amount of soup you have made, you may need to puree in two batches. A standard blender has a capacity of seven cups, but it is best not to puree more than five cups of soup at a time.

STRAINER

Even after pureeing, many soups will still contain stray bits of vegetable solids. You can leave the soup as it is, but for a more refined texture it is best to remove these tiny pieces.

We tested a variety of strainers to see which is best for this job. With its three layers of fine mesh, a chinois (a conical French strainer used in many restaurants) proved too fine. We found that the fine mesh holds back almost all of the solids and the resulting soup is too brothy. A regular mesh strainer holds back too little. In our opinion, it does no good to pass a pureed soup through a typical mesh strainer. We had the best results when we turned to a fine, round mesh strainer (see figure 1). It removed large bits of vegetables but allowed the pureed solids to pass through with the liquid.

Written by the editors of "Cook's Illustrated", American Test Kitchen, USA, 2009, excerpts chapter 4. Digitized, adapted and illustrated to be posted by Leopoldo Costa.