This isn't a traditional miso soup by any means, but it is quick and very tasty. Instead of the typical dashi made with kombu, I just used to a homemade light vegetable stock. If you're going to use a pre-made stock, make sure you use one that's not very salty as you'll be adding salty miso paste to it.
Total time: about 20 minutes
6 C light vegetable stock (I use this recipe)
1 lb firm tofu, drained, sliced into 3/4-inch cubes
6 oz mushrooms of your choice (I like oysters and shiitakes), sliced
5 oz fresh spinach
1 Tbsp miso paste (I used an organic brown rice miso)
1 scallion, green parts roughly sliced and pale green parts finely sliced
Heat the vegetable stock in a medium pot over medium heat. Once warm, ladle some of the stock into a small bowl and whisk in the miso paste; set aside. Add your mushrooms to the pot and cook until tender, about 8-10 minutes. Add the tofu and spinach and stir until the spinach wilts. Remove from the heat, return the miso and broth mixture to the pot, and divide the soup between bowls. Top with the sliced scallion and serve. Serve with a side of rice or these spicy green beans.