• Soak the bamboo skewers in water.
  
• In a mixing bowl, whisk together the joshinko and shiratamako.
  
• Slowly pour in the boiling water, stirring as you go.
  
• When the mixture begins to clump, stop adding water and knead until the dough is completely smooth.
  
• Shape the dough into a ball, then divide it into as many equal pieces as you’d like dumplings.
  
• Roll each portion into a smooth, even ball.
  
• Set a bowl of ice water nearby.
• Gently drop the dumplings into a large pot of boiling water. Stir occasionally with chopsticks to help them keep their shape.
  
• When the dumplings float to the surface, let them cook for 2 more minutes, then transfer them to the ice bath.
  
• Once chilled, drain well and place the dumplings on a damp tray to prevent sticking.
  
• Thread three dumplings onto each soaked skewer.
  

Make the glaze

• Off the heat, combine the sugar, mirin, soy sauce, water, and potato starch in a saucepan.
  
• Stir until the starch dissolves and the mixture is smooth.
• Place over medium heat, stirring constantly, until the sauce thickens to a glossy glaze. Remove from the heat.
  

Serve

• Generously spoon the hot glaze over the skewered dumplings and enjoy right away.