If I have time to invest 10 minutes in preparation (sad to say, it's not always the case, though I'm trying to do better), here's what I do -
2 cups water
1 carrot, peeled and thinly sliced
2 green onions, thinly sliced
1 dried mushroom
1 tablespoon wakame flakes
~ 1/4 cup cubed tofu (any kind will work)
1/4 teaspoon grated ginger
1 rounded tablespoon red miso
In a small/medium saucepan, combine water, sliced carrots, sliced green onions, mushroom, and wakame flakes. Bring to a boil and remove from heat. While you are waiting for the water to boil, combine ginger, miso, and a splash of water (maybe 1 tablespoon) in a small cup or bowl and mix until the miso is creamy/dissolved. After you remove the water/veggies from the heat, stir in the cubed tofu and the ginger/miso mixture. Spoon into two bowls and enjoy!
The next option is for those times when you're feeling a bit peckish in between meals and want to have something healthy and warming to tide you over until lunch or dinner.
Super-Quick Miso Mug
2 teaspoons red miso
a pinch of ground ginger
Boil some water in a teakettle. While you wait for it to heat up, combine ginger, miso, and a splash of water (maybe 1-2 teaspoons) in a mug and mix until the miso is creamy/dissolved. Pour hot (almost boiling but not quite) water over the top to fill the mug.