This sweet and savory Vegan Japanese Sweet Potato Miso Soup is a taste of fall in Japan but prepared without the traditional bonito and kombu dashi! It only takes 5 ingredients to make but the flavors are very comforting and complex; savory, umami-rich and naturally sweet! This is one of my favorite miso soups that I make in fall.Yield: 4 large or 6 medium portions
Prep Time5 minutesmins
Cook Time25 minutesmins
Inactive Time10 minutesmins
Total Time40 minutesmins
Course: Soup, Sides
Cuisine: Japanese
Servings: 4
Author: Plant-Based Matters
Ingredients
4cupspurified water
2small to medium Japanese sweet potatoes2 pcs = about 11 oz / 300 g
1cupthinly sliced yellow onion1 cup = about 1/4 of medium onion
4 1/2tbspyellow/brown koji misoor your choice of miso, adjust to taste
Leave the skin on (or peel if you like) and cut off the ends. Then, slice into 0.5 inch /1 cm disks then cut in half (half-moon.) Transfer to a large prep bowl and pour enough water (not listed in the ingredients) for the potatoes to submerge. Let it stand for 10 minutes. If the water is turning brown quickly, replace the water as necessary.
Meanwhile, prepare the onion and scallions. Set it aside.
After the soaking, drain to discard the water. In a medium sauce pan, combine purified water, drained Japanese sweet potatoes, and onion. Cover and cook over medium to medium-high heat until a gentle boil.
When it’s almost boiling, reduce the heat to medium low. Continue to simmer until potatoes are fully cooked, soft, but not broken down. You can stick a skewer (or a toothpick) to check the doneness.
Turn off the heat. Add miso to the soup. To do this, place the miso on a ladle then partially submerge the ladle in the soup. Use chopsticks to slowly incorporate the cooking water into the ladle so miso can dissolve.
Turn the heat back on at medium to medium high to reheat it (never boil!)
Serve with scallions on top. Sprinkle some shichimi pepper for some aromatic heat (optional.)
Notes
Japanese Sweet Potato
Japanese sweet potato has a red-ish purple skin, pale yellow flesh, sweeter and firmer texture than typical American sweet potatoes.
The skin can be on or off.
After slicing, some black spots may appear due to an oxidization. Those spots are unharmful and edible but may have some bitterness. To remove the bitterness as well as to reduce the discoloration, soak in water for about 10 minutes. Also, the ends tend to be tough and bitter so I recommend cut them off before slicing.
Don’t cut the potatoes too small otherwise they will be broken down in the soup.
Choice of Miso
Taste profile of miso (sweetness and complexity) is completely different from one product to another. Find your favorite and adjust the amount to your preference.
My go-to multipurpose miso is koji miso (soybean-based miso with a substantial amount of rice koji) of any kind. It has a nice balance of savory and natural sweetness from koji.
Blended miso (of a couple of different types of miso, e.g., yellow and red miso blend) is also a good option. Red miso alone may not be recommended for this recipe.
Cooking Tips
To extract the flavors of the Japanese sweet potatoes and onion into the soup, start cooking in the cold water and cook slowly at medium heat.
Never boil miso soup to retain the taste of miso at its best.
How to Store
Although, miso soup tastes the best when freshly made, you can store the leftover in a container with lid and keep in the fridge. Consume within 2-3 days.
Leftover miso can become saltier. If so, add water to dilute to adjust the taste as necessary.