• Gather all the ingredients.
  
• Cut off the stems of 4 shiitake mushrooms. Then, thinly slice the caps.
  
• Trim off the very ends of 1 small bunch fresh spinach. Chop the spinach into 2-inch (5-cm) lengths.
  

To Cook

• Add 3 cups water and 2 dashi packets to a medium saucepan. Cover with a lid and bring it to a boil on medium heat.
  
• Once the water is boiling, shake the packets with cooking chopsticks to release more flavor. Reduce the heat to medium low and cook, covered, for 2–3 minutes. Discard the packets.
  
• Add the shiitake mushrooms to the dashi and bring it to a boil. Simmer until the mushrooms are tender, about 2–3 minutes.
  
• Next, add the spinach. Stir it into the soup and gently heat until it starts to wilt, about 30 seconds. American spinach is very soft, so it cooks quickly. Then, turn off the heat. Tip: Do not overcook, as the spinach will cook more after we add the tofu and reheat the soup.
  

To Add the Miso and Tofu

• With the heat turned off, add 3 Tbsp miso to a ladleful of hot stock. Mix with chopsticks to dissolve it completely, then stir it into the broth. I use a miso muddler to measure and dissolve the paste; you can also use a fine-mesh miso strainer instead of a ladle. Now, taste the soup and add more miso, if needed. If it‘s too salty, dilute it with more water or dashi, if you have any. I added another 1 Tbsp miso since the particular type I used has a mild flavor.
  
• Cut ¼ block soft/silken tofu (kinugoshi dofu) into ½-inch (1.3 cm) cubes. Add to the miso soup. Tip: Completely dissolve the miso before you add the tofu; otherwise, the silken cubes could break when stirring in the miso. Note: It is very common to cut tofu on your palm in Japan. However, I recommend using a cutting board if you have never done this.
  

To Serve

• Gently reheat the soup until just hot. NEVER BOIL miso soup because it loses nutrients, flavor, and aroma. Once it‘s hot, turn off the heat and serve immediately in individual bowls. Place on the right side of the table setting; you can read about how to serve it at the table in my post Ichiju Sansai (One Soup Three Dishes).
  

To Store

• It‘s best to consume all the miso soup right away because it will lose its aroma and taste as time passes. Completely cool any leftover soup and refrigerate for up to 3–4 days. You also can freeze miso soup for up to 2 weeks. To reheat, bring it to a bare simmer in a pot over medium heat, but do not boil it. Miso loses its nutrients, flavor, and aroma at high temperatures.