There are countless ways to vary miso soup. You can add delicate enoki mushrooms or omit green onions in favor of bitter greens, like watercress. Since making miso soup is something new to me (though I'm trying to grow my Japanese-ish home cooking repertoire), I keep it simple, making a version that resemble what I usually see at Japanese restaurants. I stick with the basics: tofu (silken, medium, or medium-firm), wakame (a type of sea algae), and green onion.
Before making miso soup, you need to make dashi. Compared with long-simmered beef and chicken stocks, dashi comes together in no more than 15 minutes. I soaked a pieces of kombu—sea kelp—for a few minutes and then bring the kombu and its soaking water to a near simmer--just until bubbles formed around the edges of the seaweed. (The kombu I bought was quite long, so I trimmed it to one 5-inch piece and folded the rest up to store for future miso soup sessions.)
Once bubbles form, I turned off the heat and scattered dried bonito flakes—smoky tuna-like dried flakes—over the surface. Bonito flakes (also called katsuo bushi) are made from a complicated treatment involving smoking and curing that renders a piece of tuna-like fish hard enough to grate. To me, a freshly opened bag of bonito flakes smells a bit like smoked salmon. For best results, make the dashi the day you plan to use it. It keeps for a few days in the refrigerator, but it will lose some of its flavor.
- 4 (3-inch) pieces kombu
- 4 cups room temperature water
- ½ cups dried bonito flakes (katsuo-bushi)
- 2 pieces wakame, snipped into small pieces
- 4 to 6 ounces tofu, diced
- 3 to 3½ tablespoons miso (I used 1½ tablespoons each of red and yellow miso
- 1 green onion, white and light green parts only, sliced
To make the dashi: Line a fine-mesh strainer with muslin or cheesecloth. Heat the kombu and soaking water over medium-high heat until the water starts to nearly simmer. Remove from the heat and scatter the bonito flakes over the surface.
After 3 to 4 minutes, strain the dashi. (It’s OK if the bonito flakes haven’t fully dissolved.) You will have about 3½ cups of dashi.
To make the miso soup: Soak the wakame until softened, 5 to 15 minutes, depending on the wakame. (It will unfurl and become tender enough to bite.) Drain.
Bring the dashi to a boil over high heat. Add the tofu and cook for about a minute to heat through. Spoon a small amount of dashi in a heat-proof bowl and whisk in the miso to make a slurry. Stir the slurry into the dashi and taste, adding more miso to the soup if needed to boost flavor. Add the wakame and simmer for 30 seconds more.
Soak the green onion in cold water to remove some of its pungency. Drain and divide among the bowls. Pour the soup into the bowls, dividing up the tofu and wakame evenly among the servings.