Using a stockpot, warm the oil over a low to medium-low heat and add in the chopped onion. Sweat the onions. That is, cook them until they are translucent, but not browned. About 10 minutes. This will give them a subtle sweetness.
Add the minced garlic and cook for 1-2 minutes. Stir frequently to prevent the garlic from frying. Add in the grated ginger and saute for about a minute.
Add in the sliced mushrooms and saute them just so they evenly browned, adding more oil if needed.
Add ⅓ of the broth and the miso paste. Bring it to a simmer to fully incorporate the miso. I do it this way as warming up a portion of the broth is a lot faster than bringing all six cups to a simmer.
Once the paste has incorporated, add the remaining broth and bring it to a simmer.
Now add in the tofu.
When the soup begins to simmer again, add in the kale and chopped scallions (green onions). Remove from heat and serve.
This soup can easily be made ahead of time. Just follow the recipe up to adding the tofu and refrigerate. When you are ready to serve, reheat, and then add in the kale and scallions. This way, the greens stay fresh and tasty.Enjoy!