You can make a good soup with water, but stock or broth can enrich the flavor very nicely, so it's great to keep it on hand in your pantry or freezer. Veggie stock concentrate is easy to make—below is a no-cook, no-strain fantastic recipe.
If you have the time, it's easy and cheap to make great meat broth by simmering leftover bones and aromatic vegetable bits for a couple of hours and then straining and freezing the stock.
It's shocking, but almost all store-bought stock has a minuscule amount of meat broth, according to research by America's Test Kitchen/Cook's Illustrated Magazine. Beef stock is required by law to have only one ounce of beef in a gallon, but chicken stock has no minimum requirement at all! Not only that, virtually all packaged stocks and broths are reconstituted from concentrate that mostly comes one factory in Missouri. Welcome to 21st century processed food. The umami, meaty, flavor is generated from a combination of amino acids called glutamates and nucleotides, chemicals extracted from soy beans, yeast and other foods. Off-the-shelf stock is undeniably convenient, and if you are going to use it, ATK recommends Better Than Bouillon concentrate—it's the same thing as what's in a carton at a fraction of the price, plus you make only as much as you need, it keeps in the fridge forever, and it's almost vegetarian. But it doesn't have the nutrition of the real thing.
Amazing Vegetable Broth Concentrate
This adaptation of a Cook's Illustrated recipe is fantastic. Instead of cooking pounds of vegetables in water, only to have to tediously mash, strain and discard them, you can make a kickass uncooked soup base from mostly root vegetables and keep it in your freezer to use any time.
2 leeks, white and light green parts, cleaned and chopped roughly
2 carrots, peeled and chopped
½ small celeraic root, peeled and chopped
½ cup chopped parsley
3 tablespoons dried minced onions
2 tablespoons kosher salt
1 ½ tablespoons tomato paste
3 tablespoons soy sauce
Put leeks, carrots, celeriac, parsley, onions and salt in a food processor and create a paste, scraping sides frequently for 3 to 4 minutes. Add tomato paste and process and scrape for 1 minute, add soy sauce and process and scrape one more minute.
Store packed in a wide-mouth jar in the freezer. It doesn't get hard so you can use 1 tablespoon per cup of hot water to make any amount of great veggie stock.