Place the chicken breast flat on a cutting board. Place one hand on top and, with a sharp knife, slice through the chicken breast horizontally, making two equal portions for each breast.
Combine the batter mix from the meal kit with 10 tablespoons water and whisk until smooth. Place the panko breadcrumbs on a plate or in a shallow bowl. Heat the Katsu sauce in a small saucepan. Coat the chicken in batter, then roll in the breadcrumbs.
Add enough oil in a large skillet to come up ¼ inch. Heat over medium-high heat until it begins to shimmer. Fry for 3-4 minutes per side or until golden brown and the chicken reaches an internal temperature of 165°F. Toss the cooked chicken in the Katsu sauce.
Serve over rice topped with green onions and pickled ginger.
The chicken can also be cooked in an air fryer; spray with oil and place in an air fryer preheated to 400°F. Cook for 12 minutes, flipping halfway through.