• Before You Start…Please note that this recipe requires 15 minutes of resting time. 

  Gather all the ingredients.
  

To Boil the Potatoes

• Wash 2 lb russet potatoes under cold running water. Peel them and remove the eyes. Cut each potato into 4 equal pieces so they cook evenly. Nami's Tip: I use russets for their starchy, fluffy, and light texture. They are the best variety for soaking up the juices and flavor from the meat and onion.
  
• Put the cold running water and potatoes in a large pot and cover with a lid slightly ajar to prevent boiling over. Turn on the heat to medium and bring it to a boil; this will take about 15 minutes. Once boiling, reduce the heat to maintain a gentle boil and cook until done, about 15–20 minutes. You have 30 minutes to complete the next step!
  

To Cook the Onions and Meat

• Meanwhile, prepare the onion and ground beef. Mince 1 onion finely (called mijingiri in Japanese). Lay an onion half on the cutting board, flat side down. Make ¼-inch vertical slices to within ½ inch of the root end. Then, make ¼-inch horizontal slices, again keeping the root intact.
  
• Make perpendicular cuts down through the vertical slices. If you need to chop the onions finer, run your knife through them using a rocking motion while holding down the tip of the knife.
  
• Preheat a large skillet on medium heat. Once it's hot, add 1 Tbsp neutral oil and the minced onions. Spread the onions and let them cook undisturbed for a while to develop a nice char—just be careful not to burn them.
  
• Sauté until translucent and tender, about 12–15 minutes. Add 1 lb ground beef to the pan and break it up with a wooden spoon. Nami's Tip: Be sure to evaporate any moisture from the onions; excess liquid can make the croquettes soggy.
  
• Season with ½ tsp Diamond Crystal kosher salt and ¼ tsp freshly ground black pepper. Stir and cook until the meat is no longer pink. Turn off the heat and set aside until the potatoes are done cooking.
  

To Combine the Potatoes and Meat

• To check if the potatoes are cooked, insert a skewer into a bigger piece; it's done if it pierces easily. Remove from the heat. Hold the lid slightly ajar to keep the potatoes in, and carefully drain off all the water.
  
• Move the pot back to the stove over low heat. Continuously shake the pot to evaporate the remaining moisture from the potatoes, about 1–2 minutes. The potatoes should look powdery and dry. Transfer them to a large bowl.
  
• Mash the potatoes with a potato masher while they are still hot, allowing the steam to escape. Keep some potato chunks for texture. Then, add 1 Tbsp unsalted butter, ½ tsp Diamond Crystal kosher salt, and ¼ tsp freshly ground black pepper and combine gently.
  
• If the meat mixture has released excess liquid, tilt the pan to collect it on one side and avoid adding it to the potatoes. Add the drained meat to the bowl of potatoes and gently mix to combine.
  

To Make the Patties

• While the mixture is still warm (but not hot), form oval-shaped patties 3 inches (7.5 cm) in length. Try not to create air pockets that can make the patties explode while deep-frying.
  
• Place the patties on a tray or plate to let cool completely. Once cool to room temperature, cover and rest them in the refrigerator for 15–30 minutes. Do not skip this step! Nami's Tip: Chilling the patties helps the ingredients meld and prevents the croquettes from bursting during frying. Warm patties generate steam as they heat up, which can rupture the panko coating and cause them to explode. Cold patties, on the other hand, minimize steam and stay intact.
  

To Bread the Croquettes

• Prepare separate trays for ½ cup all-purpose flour (plain flour) and 2 cups panko (Japanese breadcrumbs). Crack 3 large eggs (50 g each w/o shell) into a small bowl and beat with a whisk.
  
• Dredge each patty in flour and shake off the excess. Dip in the beaten egg, then coat with the panko. , pressing to adhere the breadcrumbs.
  
• Gently press the croquettes to help the breadcrumbs adhere and adjust the shape as needed.
  

To Deep-Fry

• Add 4 cups neutral oil to a medium pot and bring it to 340–350ºF (170–180ºC) over medium heat. Use a cooking thermometer to check the oil temperature so there‘s no guessing. Nami's Tip: Make sure there‘s at least 2 inches (5 cm) of oil in the pot so the croquettes are completely submerged while cooking. Once you get used to deep-frying, you can use the chopstick or panko tricks to determine if the oil is ready.
  
• Deep-fry 2–3 croquettes at a time until golden brown, about 2–3 minutes. Do not touch or flip the croquettes until one side is golden brown. The inside is already cooked, so you just need to fry the breading. Nami's Tip: Do not crowd the pot as the oil temperature will drop quickly and cause the food to absorb more oil.
  
• Transfer to a wire rack or a plate lined with paper towels to drain the excess oil. Continue deep-frying the rest of the patties.
  

To Serve

• Serve with tonkatsu sauce (bottled or Homemade Tonkatsu Sauce). In Japan, we typically serve deep-fried foods with shredded green cabbage. I shred it with a julienne slicer or stainless steel cabbage slicer and serve it with Japanese Sesame Dressing. I also add a few wedges of tomato for color.
  

To Store

• Store the leftovers in an airtight container and freeze up to a month. To reheat, put the defrosted or frozen croquettes on a baking sheet lined with aluminum foil or parchment paper. Bake at 350ºF (180ºC) for 15–20 minutes if defrosted or 45 minutes if frozen. Check if the inside is warm before serving.