f you're making soup, gravy or any recipe that calls for broth, and you don't have any on hand, you can run out to the store (kind of a pain and and how tasty is that commercial veg broth anyway?) or use plain water (won't do much for the flavor of your dish). Maybe you have a bouillon cube, but it's so high in sodium with no compensating nourishment.
I've found a solution using the containers of miso paste that I keep in my refrigerator at all times. First I boil water to equal the amount of broth I need, and then I add miso paste--starting with a teaspoon per cup of liquid and increase the miso to taste. Stir and smash the paste in the hot liquid until it is completely dissolved, and add it to your recipe. You can experiment with white, yellow, red, etc. miso or just use whatever you have. The miso seems to enhance the flavor of many dishes.