Bring a pan of lightly salted water to the boil and cook the potatoes for 15 minutes until tender. Drain well then roughly mash with the butter seasoning with a little ground black pepper… do not mash the potatoes until smooth, keep a rough texture. Transfer to a mixing bowl.
Meanwhile place the seabass onto a foil lined grill rack and drizzle with the lemon juice. Cook under a preheated hot grill for 4-5 minutes until opaque and cooked through. Allow to cool for 2-3 minutes. Meanwhile add the lemon rind, capers and lemon thyme to the potato and mix well. Flake the cooled fish and add to the potatoes and gently fold through taking care not to break up the fish too much more.
Divide the mixture into 4 and shape into pattys. Place the flour onto a plate, the beaten egg onto another and the cornmeal mixed with plenty of freshly ground black pepper and a little salt onto another. Lightly coat the patty in the flour, then lightly coat in the egg and finally in the seasoned cornflour. Place onto a baking sheet and place in the fridge to cool for 10 minutes.
Heat the oil in a large heavy based frying pan and cook the fishcakes for 5-6 minutes, turning once until golden on both sides and piping hot, turning to cook their sides as well. Serve hot with tartare sauce if liked.
Guideline daily amounts are calculated for a standard adult woman.