Creamy Mashed Potatoes with Shio Koji

1. Gather all the ingredients.
2. Peel 1½ lb russet and Yukon Gold potatoes and remove the eyes.
3. Cut each potato in half lengthwise and then cut into rough chunks, about 2-inch cubes.
4. Transfer to a pot of cold water to soak for 2–3 minutes.
5. Drain water and rinse the potatoes under cold running water. Use the lid of the pot to hold back the potatoes when draining.
6. Add cold water about 1 inch above the potatoes. If you are not using shio koji, sprinkle 1 tsp Diamond Crystal kosher salt into the water to season the potatoes. Put the lid on, leaving a small gap, and bring to a boil over medium-high heat (it’ll take about 10–15 minutes to boil).
7. Once boiling, reduce the heat to medium (or even lower heat to maintain the boil). Cook the potatoes until tender, about 15 minutes (I usually cover the lid, slightly ajar, so water won‘t evaporate too fast.
8. Meanwhile, in a saucepan, heat 2 Tbsp unsalted butter, ¼ cup heavy (whipping) cream, and 2 Tbsp 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).
9. When a skewer goes through the potato easily, turn off the heat. Drain the water completely.
10. Rinse under hot running water and drain. Repeat 1–2 times to wash away the excess starch. Drain really well.
11. Put the pot back on the stove and let them dry for a few minutes on low heat. With a stainless steel potato masher, mash the potatoes until you have a creamy and even mash.
12. Pour the warm butter mixture over the mash and fold gently with a silicone spatula to combine.
13. Season to taste with freshly ground black pepper and salt (if you are not using shio koji). Transfer to a serving bowl.
14. Using a spoon to create grooves and top with 1 Tbsp unsalted butter, a few stalks chives (chopped), and more freshly ground black pepper. Enjoy!

To Store

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