Pound 270g of boneless skinless chicken breast to an even ½in / 1cm thickness. Season with ½ teaspoon of kosher salt and ⅛ teaspoon of black pepper.
Whisk 1 large egg with ½ tablespoon of neutral oil. Coat the chicken in 3 tablespoons of all-purpose flour, dip it in the egg, then press it into 1 cup of panko.
Heat 3 cups of neutral oil for deep-frying in a deep pot to 340°F / 170°C; it should be about 1½in / 4cm deep.
Fry for about 3 minutes, turning halfway, until golden and the chicken reaches 165°F / 74°C. Drain on a wire rack, slice and serve with tonkatsu sauce.
