Bring 2 quarts of water to a boil in a 4-quart saucepan
. Add the fried tofu
for 10 minutes. Add the squash and simmer for another 15 minutes. Add the remaining ingredients, except for the miso and scallions
, reduce the heat to low and simmer, covered, for about 10 minutes. Remove from heat.
In a small bowl, whisk together the miso and 1/2 cup water until the mixture is smooth and thinned out, then add the miso to the pot. Stir well and serve immediately, garnished with the scallions.