• Gather all the ingredients. For the cooked rice, please note that 1½ cups (300 g, 2 rice cooker cups) of uncooked Japanese short-grain rice yield 4⅓ cups (660 g) of cooked rice. See how to cook short-grain rice with a rice cooker, pot over the stove, Instant Pot, or donabe.
  
• Remove and discard the seeds from 3.5 oz pickled plums (ko ume).
  
• Mince the plums with a sharp knife.
  
• Add the chopped pickled plums and 2 Tbsp toasted white sesame seeds to 4⅓ cups cooked Japanese short-grain rice.
  
• With a rice paddle, mix well together using a cutting motion. Don’t “stir“ the rice and make it mushy. Roughly divide the rice into 6 or 8 equal portions.
  

To Shape the Rice Balls

• Prepare a bowl of water and a bowl of 1 tsp Diamond Crystal kosher salt. Wet both hands and then dip 2 fingertips in the salt and spread between your palms.
  
• Scoop the rice onto your palm. Gently press and form the rice into a triangle. I use three fingers (thumb, index finger, middle finger) to make a triangle corner. Tip: For step-by-step photos and instructions on how to shape the rice balls using your hands, an onigiri mold, or plastic wrap, see my Onigiri recipe.
  
• When you press, your hands should be just firm enough so the rice ball doesn‘t fall apart. You don‘t want to squeeze the rice too tight.
  
• Wrap the rice balls with strips cut from 3 sheets nori (dried laver seaweed). Enjoy!