As much as I love a hamburger, it’s not something I cook at home because there are so many good ones available in restaurants. This Japanese burger is filled with chicken karaage, with pan-fried compressed rice instead of a hamburger bun.
It can be difficult to find boneless chicken thighs - often, it's the thigh and drumstick together. The drumstick has a lot of sinew, which isn't good for this recipe, which is why I buy the bone-in thighs and remove the bone myself. But if you can find boneless thighs without the drumstick attached, then use them - it will save a little time.
Shape the rice buns first, because they need to be cold before they are pan-fried. Heat the cooked rice, either in the microwave or by steaming it. Divide the rice into eight portions. Line a round mould that’s about 9.5cm (3¾in) in diameter with cling film, using enough that it comes up the sides of the mould with about 2cm (⅞in) of overhang.
Scoop a portion of the rice into the mould. Press firmly so the rice is shaped into a tightly compressed flat disc that’s about 5mm (¼in) thick. Grasp the overhang of the cling film and lift out the rice disc. Take the disc from the cling film and place it on a lightly oiled baking tray. Shape seven more rice discs in the same way, then cover with cling film and refrigerate for at least an hour.
Put the bone-in chicken thighs skin-side down on the cutting board. Using a very sharp paring knife, slice into the thigh along the length of the bone. Use the tip of the knife to cut away the meat from the bone in one piece, taking care not to slice into the skin. Dry the boneless thighs with paper towels.
Roughly chop the garlic. Put the chicken in a bowl and add the soy sauce, rice wine, garlic, ginger and white pepper and mix thoroughly. Leave at room temperature for about an hour.
Pan-fry the rice buns. Pour a thin layer of oil into a skillet and place it over a medium flame. When the oil is hot (about 90 seconds), add the chilled rice discs; you’ll need to cook them in batches. Pan-fry the discs until pale golden on one side, then carefully flip them over and cook the other side, adding more oil to the skillet if needed. Place the pan-fried buns on a clean, dry tray.
Sprinkle the cornstarch over the chicken thighs and marinade and mix well. Pour oil to the depth of about 1.5cm (⅔in) into the skillet used to pan-fry the rice buns (no need to wash it). Heat the oil to 170°C (340°F). When the oil is hot, fry the chicken thighs for about six minutes, or until cooked through, turning them over once or twice in the hot oil. Drain on paper towels.
Shred the cabbage, then pile some of it onto four of the rice buns. Add a zigzag of the Kewpie mayonnaise and a light sprinkling of shichimi togarashi. Place a fried chicken thigh on the cabbage, then top with the second rice bun. Serve immediately, with the remaining shredded cabbage on the side