First de-bone and fillet the whitefish, then chop it into relatively small pieces. In a large bowl, combine the whitefish, whitefish salad, onion, cheese, lemon zest and juice and 1/4 cup Panko bread crumbs. Season to taste with pepper and mix well. Sprinkle remaining Panko on a plate, divide the whitefish mixture into four and shape into cakes, coating them lightly with the Panko. (If making ahead, put on a plate, cover with plastic wrap and refrigerate until needed.) To cook, heat the oil in a large heavy-bottomed sauté pan over medium heat. Add the fish cakes and fry for 5-6 minutes. Turn and cook the other side for about 4-5 minutes. Allow cakes to rest 5 minutes before serving.
Picture with kale, halved cherry tomatoes, olive oil, and salt.