Butterfly the plaice by cutting down the backbone, open the fish like a book and cut it into a half widthwise.
oil the potatoes until just soft (about 10 minutes), drain and slice into even-sized pieces.
Heat the butter in a large frying pan and lightly fry the plaice fillets on both sides until crisp and golden. Place onto a warmed serving platter and keep warm.
Place the pan back onto the stove over medium heat.
Add the spinach, parsley, shallots and garlic to the pan and sauté until just wilted. Add the butter, juices from the pan and lemon juice and zest.
Spoon the mixture on top of fillets and boiled potatoes, serve and enjoy!
Serving Suggestions: Serve with fresh lemon wedges and flat-leaf parsley.