• Gather all the ingredients. Bring a big pot of water to a boil. [Optional] If your sesame seeds are not toasted/roasted yet, or if you want more toasty taste/fragrance, put sesame seeds in a frying pan and toast them on low heat. When 2–3 sesame seeds start to pop from the pan, remove from the heat.
  
• While waiting for the water to boil, add 1 Tbsp mirin to a small saucepan. Cook it over medium heat until the alcohol is evaporated, roughly 30 seconds. Set aside.
  
• In a suribachi (mortar), add 2 Tbsp toasted white sesame seeds and grind with a surikogi (pestle) until the sesame seeds are almost ground. It’s nice to leave some texture.
  
• Add 2 tsp miso, 1 tsp sugar, the alcohol-free mirin, and ½ tsp soy sauce and mix well together.
  
• Once water is boiling, add ¼ tsp Diamond Crystal kosher salt. Hold 6 oz spinach leaves so you can start blanching from the stem (which takes longer to cook). Cook for 15 seconds. Let go the leafy part and cook for 30 seconds.
  
• Remove spinach from the water and soak in iced water to stop the cooking. Alternatively, drain and run the spinach under cold running water until cool.
  
• Collect the spinach and squeeze the water out.
  
• Cut the spinach into 2-inch (5-cm) lengths and add to the bowl.
  
• Mix the spinach and sauce together. Serve at room temperature or chilled.
  

To Store

• You can put it in an airtight container and store it in the refrigerator for 2–3 days or in the freezer for 2–4 weeks.