Creamy Mashed Potatoes with Shio Koji

Looking for a new way to enjoy mashed potatoes? Try it with Shio Koji! Buttery, creamy and umami-packed, these mashed potatoes with shio koji have a Japanese flair to the classic recipe. 
This recipe is created by Nami( Just One Cookbook®)
Prep Time 20 minutes
Cook Time 30 minutes
Servings 4


  • 1 ½ lb A combination of Russet and Yukon Gold potatoes (should be one Russet potato and one Yukon potato)


  • 2 tbsp Unsalted butter
  • 1/4 cup Heavy whipping cream
  • 2 tbsp SHIO KOJI
  • Freshly ground black pepper


  • 1 tbsp Unsalted butter
  • A few stalks chives
  • Freshly ground black pepper


  • Peel potatoes and remove the eyes. Cut each potato in half lengthwise and then cut into rough chunks, about 2 inches cubed. Transfer to a pot of cold water to soak for 5 minutes. Drain water and rinse the potatoes.
  • Add cold water about 1 inch above the potatoes. Put the lid on, leaving a small gap, and bring to a boil over medium-high heat. Once boiling, reduce heat to medium and cook the potatoes until tender, about 15 minutes.
  • Meanwhile, in a saucepan, heat the butter, heavy cream, and shio koji over medium-low heat. Turn off the heat and set aside to keep warm (you may need to reheat before adding to the potatoes).
  • When a skewer goes through the potato easily, turn off the heat. Drain the water completely. Rinse under hot running water and drain. Repeat 1-2 times to wash away excess starch. Drain really well.
  • Put the pot back on the stove and let them dry for a few minutes on low heat. With a potato masher, mash the potatoes until you have a creamy and even mash.
  • Pour the warm butter cream mixture over the mash and fold gently with a silicone spatula to combine. Season to taste with freshly ground black pepper. Transfer to a serving bowl. Using a spoon to create grooves and top with a slice of butter, chives, and more freshly ground black pepper. Enjoy!

 To Store 

  • Mashed potatoes keep for 3 days in the refrigerator. You can also freeze them for a month in an airtight container or freezer bag.

Product used in this recipe

re sq 63473 Hikari Miso Shio Koji 20.40oz

Shio Koji
20.4 oz (580 g)

Shio Koji is a traditional Japanese ingredient made with a fermented rice malt (koji) and salt (shio). The enzymes contained in shio koji break down proteins to draw umami out of meat and fish. Shio Koji is in liquid form with the tiny half-dissolved grains of rice malt and packaged in a convenient plastic bottle.

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