Place the potato in a saucepan of cold, salted water and bring to the boil. Cook for 20 minutes or until tender. Drain and allow to cool slightly. Place the mayonnaise and chives in a bowl and stir to combine. Add the potato and toss to coat. Set aside.
Brush the fish with half the melted butter and press into the breadcrumbs. Place on a lightly greased baking tray and cook under a preheated hot grill (broiler) for 2 minutes. Turn, brush with the remaining butter and cook for a further 2 minutes or until golden and cooked through. Serve the fish fingers with the potato salad and lemon wedges. Serves 4.