Preheat the oven to 400 degrees F and lightly coat a large casserole dish or baking dish with cooking oil. As an alternative, you can line a baking sheet with parchment paper.: The air in the oven will feel warm and steady as it reaches 400 degrees F , a temperature that encourages rapid browning. You want a fully heated environment so the coating starts crisping immediately, creating a golden surface. One common mistake is placing the chicken into an oven that is still warming, which can lead to soggy crusts. If you notice any dampness on the crumbs, allow an extra minute of heat before inserting the dish so the exterior begins firming up right away.
Slice the chicken breasts through the center to create four thinner cutlets from two boneless chicken breasts in order to get even thickness throughout the chicken filets. This is an important step, as it helps the chicken cook through evenly without becoming over-cooked and omits the need to tenderize the chicken with a meat tenderizer.: When you slice the chicken , you should feel a smooth, dense texture that flattens slightly under your knife. The visual cue is uniform thickness across each filet, which ensures even heat penetration so the center reaches proper doneness without drying. A frequent error is leaving one side thicker, causing uneven cooking. If your knife slips or the breast is uneven, gently press with your palm to even it before slicing again.
Crack the egg into a shallow bowl and whisk it until it is well-beaten. Transfer the breadcrumbs, flour, salt and pepper to a large plate and stir it around with a fork until everything is well-combined.: The beaten egg should look glossy and slightly frothy, signaling air folded into the mixture so it adheres smoothly. The dry mixture should be evenly distributed, with flecks of sea salt and black pepper visible in the crumbs. This balance prevents pockets of unseasoned coating. A common slip is under-mixing the crumbs, which leaves uneven seasoning. If you see clumps of flour, fork them apart until the texture is uniform.
Dredge a chicken cutlet in the beaten egg mixture, then coat it liberally in the breadcrumb mixture, making sure to get both sides. Repeat for the rest of the chicken.: As you dip, the egg should form a thin wet film that anchors the crumbs. Press the crumbs gently so they adhere, and lift the piece to let any excess fall away. You should hear a faint brush of crumbs landing, and the cutlet will feel slightly textured to the touch. A typical mistake is skimping on the egg which causes patchy breading. If the crumbs seem loose, press again and let the coated pieces rest briefly to set the bond.
Transfer the breaded chicken cutlets to the prepared baking dish and bake for 12 to 15 minutes, or until the chicken reaches an internal temperature of 165 degrees F and the outside is nice and crispy.: During baking you will see the coating transition from pale to a warm golden brown and you may hear a faint crackle as moisture leaves the crust. The aroma becomes toasty and enticing. Use a thermometer to ensure the center hits 165 degrees F , which guarantees safety while preserving juiciness. Avoid opening the oven repeatedly, as temperature loss can slow browning. An overbaked cutlet will feel firm and dry when pressed, so err on the side of checking temperature early.
While the chicken is baking, stir together the ingredients for the sauce in a small bowl until creamy and well-combined.: As you whisk the mayonnaise , soy sauce , honey , and sriracha , the mixture should emulsify into a glossy, smooth sauce that smells both sweet and spicy. Taste and adjust the heat or sweetness to balance the kick, and refrigerate briefly if you want the flavors to meld. A common misstep is adding too much hot sauce at once; add a little, taste, then add more so the balance stays intact.
Serve the baked chicken katsu with your choice of sides along with the spicy honey sriracha mayo.: The final plate should present chicken with a golden crust, the sauce spooned or drizzled to one side, and sides that complement without overwhelming. When you cut the cutlet, the inside will be moist and tender and the coating will still be crisp. Avoid letting the cutlets sit too long before serving, as steam can soften the crust. If reheating leftover pieces, use the oven to revive crispness rather than the microwave.