I love to make soups in the winter, and have often written about the wonders of homemade broth. I’ve never cared much for any vegetable broth that I have tasted, and I like the deep savoriness and the economy and thrift of making meat and chicken broth. But recently, more or less by accident, I did discover an alternative. I was experimenting with my abundant supply of water kefir, and was cooking it down to make a syrupy glaze of the type that I have enjoyed making out of kombucha. About the original idea, all I can say is please don’t try this with kefir, because the result is rather dreadful. However, having tasted the product of one pot, I turn the heat off under the other one, which had been reduced to a little more than half its original volume. I tasted, thought, added some salt, and had something that tasted savory and surprisingly like chicken broth. Cooked with some aromatics and herbs, the resemblance would be even more striking.
I tried the same experiment with some water kefir made with coconut sugar, thinking that the deeper color and flavor would be attractive in this context. But to my surprise, the faint bitterness that is detectable as an undertaste in brown sugar or coconut sugar was greatly exaggerated in the finished broth, to the point that I threw it out. So save yourself some time and trouble and use plain sugar when making kefir that you intend to cook down.
Since I remain obsessed with fermentation months after first reading the Noma Guide to Fermentation, I decided to try combining various fungi both microscopic and macroscopic in a mushroom broth. I had a quart of broth made from boiling down 2 quarts of water kefir. I started with butter, which made my soup vegetarian, but if you wish to use olive oil or some other vegetable oil instead it will be vegan. Heat about 3 tablespoons of your chosen fat in a small heavy sauce pan, and sauté one large or two small cloves of garlic finely chopped and one small onion sliced thin. Cook them over medium low heat, stirring frequently, until they are thoroughly cooked, soft, and a bit caramelized. Put in 3 tablespoons of mushroom powder. I used dried and powdered Sullius that I had gathered, but the most commonly available powdered mushroom is porcini. Sautée the powder for a few minutes, and add a quart of broth to your pan. Bring to a boil, and then turn the heat down to simmer. Now stir in 2 tablespoons of white miso paste. Taste for saltiness. You might want more miso, but taste it first. I am working on making my own miso, but a good grade of white miso from your nearest Asian market is fine. Simmer the soup for 15 to 20 minutes over low heat.
The final step is to smooth it out. You can do this with a stick blender, but in my opinion there is no alternative to a Vitamix blender to turn your soup into pure velvet. Make sure you know how to handle hot liquids in your blender without creating a sort of fluid explosion. When the soup is completely smooth, return it to the pan, heat gently, taste for seasoning, grind in a little fresh pepper, and serve.
There is nothing quite like the process of fermentation to produce a rich, meaty savor without the use of meat. In this basic recipe, I was experimenting with fermentation as a way to make a vegan or vegetarian product highly satisfying. But if you are not a vegan or vegetarian, there is no reason to feel limited. You can start with bacon fat if you want to, or add chunks of leftover cooked meat, or finish it with a dash of good sherry or a swirl of cream or both. Sautéed mushrooms would be a great addition.
It interested me that despite use of miso, this soup doesn’t taste identifiably Asian. It just tastes good. If you want something that leans more Asian, you could add a piece or two of kombu to the kefir for a few minutes as it cooks down and finish the bowls with some diagonally slivered scallions.