• Before You Start…Please note that this recipe requires 1+ hour of chilling time.

  Gather all the ingredients.
  
• Place a stainless steel steamer basket inside your pressure cooker (I use a 6 QT Instant Pot) and add 1 cup water to the pot.
  
• In a small saucepan, place 1 large egg (50 g each w/o shell) and cover it with water. Bring it to a boil over medium-high heat. Once boiling, reduce the heat to a simmer and cook for 12 minutes. Prepare the potatoes during this time (see below).
  
• When the egg is done, immediately discard the boiling water and cool the egg with cold water. Once the egg is cool, remove the eggshell and mash the boiled egg in a small bowl with a fork.
  
• While the egg is cooking, peel the skins of 1½ lbs large russet potatoes and cut into 1½-inch (4-cm) pieces. They should be roughly the same size so that they’ll cook at the same rate. Then, soak the potatoes in a bowl of water (if you don’t have any wait time, add them directly to the pressure cooker). By soaking the cut potatoes in water, it removes the starch and helps retain its color.
  
• Place the potatoes in the steamer basket inside the pressure cooker. Close the lid and cook at High pressure for 5 minutes. Make sure to turn the vent to the Sealing position. For an Instant Pot, select the Steam setting and set the cooking time to 5 minutes.
  
• While the potatoes are cooking, prepare the other ingredients. Cut 2 slices ham into ¼-inch (6-mm) cubes.
  
• Peel the skin of 3 oz carrot and thinly slice crosswise using a mandoline slicer. The mandoline slicer will help you achieve very thin slices of carrot. If you don’t have one, simply use a knife to cut the carrot into thin slices.
  
• Peel the skin of 2 Persian cucumbers, leaving some parts unpeeled for a striped pattern. Use a mandoline to slice the cucumber crosswise or slice thinly with a knife.
  
• Sprinkle ½ tsp Diamond Crystal kosher salt over the carrot and cucumber and rub it in with your hands. Wait 10 minutes to let them release their moisture. Alternatively, you can blanch the sliced carrot (don't blanch the cucumber) for 2–3 minutes until tender.
  
• Quickly rinse under water, gently squeeze out the water, and set aside.
  
• Once the pressure cooking is complete, you can let the pressure valve release naturally for about 15–20 minutes or manually release the pressure. Insert a wooden skewer in the center of a potato. If it goes through smoothly, then the potatoes are ready. If the skewer gets stuck in the potato, cook for a bit longer. When the potatoes are done, take out the steamer basket and transfer the potatoes to a bowl; I used a suribachi (Japanese mortar) here. Mash the potatoes with a masher or a large fork; I used a surikogi (Japanese pestle) here following my mom’s method. Don’t crush the potatoes completely and leave some small chunks for texture.
  

To Assemble the Japanese Potato Salad

• Season the mashed potato with ½ tsp Diamond Crystal kosher salt and freshly ground black pepper.
  
• Add 2 tsp rice vinegar (unseasoned) and mix it all together. Set aside to let cool.
  
• Add the mashed egg, cucumbers, carrots, ham, and 4 Tbsp frozen or canned corn to the mashed potato and mix it all together.
  
• Add 4–6 Tbsp Japanese Kewpie mayonnaise and combine well. Taste the potato salad first before adding more mayonnaise or salt.
  
• Mix all the ingredients together. Serve at room temperature or cover the potato salad with plastic and let it chill in the refrigerator for at least 1 hour.
  

To Store

• The potato salad will keep in the refrigerator for up to 1–2 days.