I have a thing where I really don't like to add chicken stock to vegetable based recipes. Or pork-based recipes. Or beef-based recipes. It seems so strange to mingle the two different flavors. I would much rather add water or vegetable stock that mimics the other flavors in the recipe. The problem is that I have never found a good vegetable stock in stores. Not only are they "not great", they are really generally pretty terrible. Like rusty-colored water with no discernible vegetable flavor. So, I am usually left adding only water (which doesn't add a whole lot to a recipe's flavor) or making my own stock, which isn't so difficult, but storing the extra is a chore. I don't really have space in my freezer for containers of vegetable stock and I don't want to have to whip up a new batch every time I need it. Then, I came across this recipe from Cook's Illustrated. A chef was presented with this same issue, noting that there was not a single store-bought vegetable stock he could recommend. So, he came up with an ingenious idea. He pureed all the vegetables you would add to the ideal vegetable stock, tinkering with the ingredients until he found the perfect mixture that would freeze well. Then, he added enough salt that the stock puree would never completely freeze solid (so that you could still scoop some out when needed) and then reconstitute with water.
So, here are the ingredients: Celery root (not celery, which will crystallize in the freezer), leek, carrots, dried onion (not onion, which will crystallize), salt, parsley, soy sauce, and tomato paste (not tomato, which will, you guessed it! crystallize).
2 leeks, white and light green parts only, chopped and washed thoroughly (2 1/2 cups or 5 ounces)
2 carrots, peeled and cut into 1/2-inch pieces (2/3 cup or 3 ounces)
1/2 small celery root, peeled and cut into 1/2-inch pieces (3/4 cup or 3 ounces)
1/2 cup or 1/2 ounce parsley leaves and thin stems
3 Tbs. dried minced onions
3 Tbs. kosher salt
1 1/2 Tbs. tomato paste
3 Tbs. soy sauce
Process leeks, carrots, celery root, parsley, minced onions, and salt in food processor, scraping down sides of bowl frequently, until paste is as fine as possible (3-4 minutes). Add tomato paste and process 1 minute, scraping down bowl every 20 seconds. Add soy sauce and continue to process 1 minute longer. Transfer mixture to airtight container and tap firmly on counter to remove air bubbles. Press small piece of parchment paper flush against surface of mixture and cover. Freeze for up to 6 months.
To make 1 cup of broth, stir 1 tablespoon fresh or frozen broth base into 1 cup of boiling water.