We've been reading about umami for years and thought we understood it, but we never really got it until a few weeks ago, when we found ourselves with a big pot of underflavored leek and potato soup. We'd made this soup at least a hundred times over the years, and although it occasionally needed an extra dose of salt, butter, or Bragg to fill out the flavor, it had always been reliably delicious.
This time we had big beautiful leeks and a fresh bag of potatoes, and we had taken care not to add too much water, just covering the sliced veggies with liquid before we turned up the heat. What happened? We still don't know, but even after we added salt, Bragg, and butter, the soup lacked flavor. We knew that if we added any more salt, Bragg, or butter, we'd just end up with a pot of salty, Braggy, fatty, underflavored soup.
Then we thought of adding miso. After all, miso and water make a fine, simple, flavorful broth. We had a small tub of sweet yellow miso in the fridge, so, using the strainer method, we stirred a couple of tablespoons into the soup. Just like that, we had flavor; just like that, we really understood the concept of umami. The miso added depth and interest without unduly amping up the salt or adding a strong miso flavor.
There are many, many kinds of miso, ranging from the mild yellow version we used to dark, beefy concoctions reminiscent of demi-glace. (All are based on fermented soybeans and completely vegetarian.) You may be able to find miso in the refrigerated section of your produce department; if not, look for it in a health food store or Asian market.
Experiment, and you'll find that miso is a delicious, easy way to add flavor to soups, sauces, and salad dressings.