About 15 minutes
With all due respect to packaged ramen, this is probably the best “instant” soup there is. At its simplest (which it is here), miso soup is basically tea: miso whisked with water. Add on if you like. Tofu and scallions are traditional, but do what you want: carrots, peas, beans, greens, sea greens, and so on, or soaked Asian noodles, chopped leftover cooked meat or seafood, or a couple cooked scrambled eggs stirred in right before serving.
1/3 cup any miso
1 ⁄ 2 pound any tofu, cut into small cubes, optional
4 scallions, chopped
1. Put 6 cups water in a large pot over medium heat. When steam rises from the surface of the liquid and small bubbles appear along the edges of the pot, ladle 1 ⁄ 2 cup of the water into a small bowl with the miso and whisk until smooth.
2. Lower the heat under the pot to medium-low and add the miso slurry; stir once or twice, then add the tofu if you’re using it. Do not let the mixture boil; let it sit for a minute or two to heat the tofu through. Stir in the scallions and serve.