2 large plaice fillets, about 175 g (6 oz) each, halved to make 4 thin fillets
25 g (1 oz) Parmesan cheese, grated
salt and pepper
mashed potato, to serve
Melt the butter in a saucepan. Stir in the flour and cook for 2 minutes. Slowly whisk in the milk until smooth. Bring to the boil, whisking, then simmer for a few minutes until thickened. Take off the heat, stir in the cheese and season.
Place the spinach in a sieve and pour over boiling water until thawed. Drain well, then roughly chop. Place the fish on a lightly greased baking sheet. Spread a layer of spinach on top of each fillet, then drizzle over some of the white sauce. Sprinkle with the Parmesan.
Place in a preheated oven, 200°C (400°F), Gas Mark 6, for 10–12 minutes until the fish is just cooked through. Serve immediately with mashed potato.