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 co…