• Gather all the ingredients. Adjust an oven rack to the middle position and preheat the oven to 400ºF (200ºC). For a convection oven, reduce the cooking temperature by 25ºF (15ºC).
  

To Toast the Panko

• Combine 1¼ cups panko (Japanese breadcrumbs) and 1 Tbsp neutral oil in a frying pan.
  
• Toast the panko over medium heat, stirring frequently, until golden brown.
  
• Transfer the toasted panko to a prep tray or shallow dish and cool.
  

To Butterfly the Chicken

• We‘ll butterfly 2 boneless, skinless chicken breasts using the Japanese cutting technique Kannon biraki (観音開き). With a sharp knife, score the chicken breast lengthwise along the top center line, cutting about halfway through the thickness of the breast; do not cut completely through.
  
• Then, turn the knife parallel to the cutting board and slice the chicken breast from the center toward the left side (or the right side, if you‘re left-handed) to make it evenly thin. Stop before you cut all the way through the edge; then, open it like a book. Imagine we‘re creating a French door here.
  
• Rotate the breast 180 degrees and butterfly the second side in the same manner from the center toward the left (if you hold the knife in your right hand), creating another “door.“
  
• Cut the butterflied breast in half down the center. Now, you have two pieces. Butterfly the remaining chicken breast in the same manner. Next, using a meat mallet or rolling pin, pound the chicken cutlets to an even thickness, about ¼–½ inch (6 mm–1.3 cm).
  

To Bread the Chicken

• Season both sides of the cutlets with Diamond Crystal kosher salt and freshly ground black pepper.
  
• Set up the breading station. In a prep tray or shallow dish, whisk together 1 large egg (50 g each w/o shell) and ½ Tbsp neutral oil. In a second tray, place ¼ cup all-purpose flour (plain flour). Line up the toasted panko as the third tray. Tip: By adding oil to the egg, the breading won't detach from the meat while cooking. It will also help seal in the chicken's juices and flavor.
  
• First, dredge a chicken cutlet in the flour and shake off any excess. Next, dip the floured chicken into the egg mixture and coat well on both sides.
  
• Finally, coat the chicken with the toasted panko, pressing firmly to ensure that it adheres well. Set aside. Bread the remaining cutlets.
  

To Bake

• Put the breaded chicken cutlets on a wire rack placed on a rimmed baking sheet. Bake at 400ºF (200ºC) for about 25–30 minutes.
  
• When the internal temperature of the chicken reaches 165ºF (74ºC), it‘s done. Remove from the oven and cut into ¾-inch (2-cm) slices.
  

To Serve

• Serve with a shredded cabbage salad (I like to use a handy cabbage slicer; you can find it on Amazon and JOC Goods), tomato wedges, and cucumber slices with a side of my Japanese Sesame Dressing. Drizzle tonkatsu sauce over the Chicken Katsu to enjoy!
  

To Store

• You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days or in the freezer for a month. To reheat, bake at 350ºF (180ºC) for 15–20 minutes for baked katsu that was thawed in the refrigerator overnight, or for 30 minutes if heating directly from frozen. Check that the inside is warm before serving.