• Gather all the ingredients.
  

To Make the Marinade

• Peel and grate 1 knob ginger and measure 1 tsp ginger (grated, with juice).
  
• In a small saucepan, combine 2 Tbsp mirin, 2 Tbsp sake, and 4 Tbsp soy sauce.
  
• Bring it to simmer over medium heat and let the alcohol evaporate for a minute. Then, turn off the heat and add 2 Tbsp miso.
  
• Whisk to combine the miso with the sauce. Then, add the grated ginger and mix all together. Set aside to let cool completely.
  

To Cut the Hamachi

• With a sharp (sashimi) knife, cut 1 lb sashimi-grade yellowtail (hamachi) into 5-mm slices.
  

To Marinate the Hamachi

• In a glass deep container (with a lid), put some marinade on the bottom and start placing some of the hamachi slices in a single layer. Then, drizzle some of the marinade on top.
  
• Place more hamachi slices on top followed by more marinade.
  
• Once you finish with all the hamachi slices, close the lid and refrigerate for 30 minutes or up to 2 hours maximum; otherwise, it gets salty.
  

To Prepare the Hamachi Bowl

• Cut 1 green onion/scallion into fine rounds.
  
• Wash 10 shiso leaves (perilla/ooba) and pat dry with a paper towel. Remove 4 leaves and set aside for serving. Roll up the remaining shiso leaves.
  
• Cut the rolled shiso into chiffonade and separate them loosely.
  
• Prepare individual bowls of steamed rice and set aside so it’s not too hot. Prepare the toppings and take out the hamachi sashimi from the refrigerator. Place a shiso leaf on top of the rice in each bowl.
  
• Place the sashimi slices on top of the rice. Garnish the bowls with ¼ tsp toasted white sesame seeds, chopped green onion, the shiso chiffonade, and sushi ginger (gari) on top. Enjoy!