In the days before microwave ovens, it was sometimes a challenging task to use the remnants of previous meals and present them again in a palatable way. My mother, who never let any scrap of food go to waste, was as inventive in using leftovers as she was thrifty. One of her favorite concoctions for using the miscellaneous tidbits that collected in the refrigerator was homemade soup. Mother kept a large pot in the refrigerator, and into the pot she tossed leftovers of all sorts: meat, gravy, broth, vegetables, beans, rice, pasta, and cooking liquid. When there were enough scraps collected in the pot to make soup for our family, she added whatever seasonings complemented the conglomeration, added extra liquid if needed, and simmered the mixture on the stove until the flavors combined in a savory blend. Mother never had a set recipe for soup. Every pot was different, as the ingredients varied according to what leftovers she happened to have, but her soups were always delectable and nourishing.

The microwave oven has made it easier to reheat leftovers and have them taste as if they were freshly made. As a consequence, I have fewer food scraps to collect in a soup pot than my mother had in the pre-microwave days. Rather than building my soups around leftovers, I often begin a pot with fresh ingredients and toss in what leftovers I have, almost as an afterthought. Many of the principles for soup-making that my mother taught me still apply, though.

The basics of homemade soup base

While commercially canned soup broth is readily available, I prefer to make my own soup stock. Not only do I like the taste of homemade stock better, but also I have the assurance that it is gluten free. Any juices that cook out of meat and any liquids used to cook meats can be reserved for stock. Corned beef broth makes delicious French onion soup. Lamb broth is especially good for making lentil soup. Ham broth is particularly well suited for bean soup and potato soup. I save even small amounts of meat juices because they can be combined with other meat juices and liquids to make broth, provided that the flavors of all the components are compatible. Meat juices and cooking liquids that will not be used within a few days should be frozen in a labeled container for later use. Leftover gravy also can be used in soup base, thinned with other liquids if it is too thick. Like other soup stock candidates, gravy can be frozen and used at a later date.

Homemade soup stock can be made by boiling the bones, fat, and skin of chicken, turkey, ham, beef, or lamb. For every 4 cups of water, add 1 teaspoon salt or 1 1/2 teaspoons vinegar to extract minerals from the bones. This makes the soup broth richer in flavor and nutrients. Simmer the mixture for at least an hour, preferably longer. After cooking, strain the solids from the broth. If time permits, refrigerate the broth to allow the fat to rise to the top and harden. Removing the hardened fat makes the broth lower in calories and more healthful, but the broth still retains the flavor components that were in the fat and skin.

Liquid drained from canned vegetables and liquid used to cook vegetables or beans make nutritious soup base all by themselves, or they can be used as an addition to meat-based stock. Canned tomatoes – whole, diced, crushed, or juice – can be used as a soup base or as a flavorful supplement to other stock.

The meat (and vegetables) of the matter

For those of us who are omnivores, any meat can be used in soups. Tough meat can receive a second chance in life by being simmered slowly in soup broth. The meat should be simmered until it is tender before vegetables and seasonings are added. Ground meat can be included in soup either crumbled or formed into meatballs. Small amounts of meat that would not be sufficient for a family meal can be supplemented by adding beans to the soup to boost the protein content. Various types of seafood can be added to beef or chicken soups to make gumbo, or they can be added to potato soup to make chowder.

Nearly any vegetable can be used in soups. A bag of frozen mixed vegetables cooked in broth makes a quick, easy vegetable soup. When using both leftover vegetables and fresh or frozen vegetables in the same soup, cook the fresh or frozen vegetables in the stock until they are almost done. Add the leftover vegetables in the last few minutes of cooking to reheat them and allow their flavors to blend in the mixture. When using broccoli, cauliflower, or cabbage in soups, do not cook them any longer than is needed to tenderize them. They contain sulfur compounds that break down with overcooking. Creamed vegetables can be used in soups. However, do not allow the soup to boil after the creamed mixture has been added, or the milk in it will curdle. To thicken soup, add leftover mashed potatoes, instant potato flakes, or pureed vegetables.

Rice and gluten-free pasta add carbohydrates to soups. When using pre-cooked rice or pasta, add it toward the end of the cooking time so that it does not get too soft. To use uncooked rice or pasta in soup, follow the package directions to determine how long it should cook in the broth. Usually, this will be 50 minutes for brown rice, 25 minutes for white rice, and 8 minutes for pasta. Because rice soaks up water as it cooks, it may be necessary to add water to the broth to make sure there is enough liquid that the soup does not accidentally become a casserole. One cup of rice requires 2 to 2 1/2 cups of water in cooking.

Finally, season soups according to taste and experiment with new seasonings. Salt, pepper, garlic, parsley, celery, and onions are basic seasonings that can be used in almost any soup. Sage, thyme, and rosemary do well in soups made with chicken or turkey stock. Try bay leaf, basil, and oregano in beef soups. With any seasoning, add a little at a time and taste to see if more is needed. This is especially important when incorporating leftovers that have already been seasoned.

Like my mother, I have no set recipe for making homemade soup. My soups are as varied as hers, depending on the ingredients I have on hand and whatever leftovers I have to contribute to the brew. Whether the soup is totally from fresh ingredients or mostly the remains of previous meals, the end result is like my mother's: an easy, nutritious meal that is especially heart-warming during the cooler months of the year.