Fish cakes with parsley sauce

Name: Fish cakes with parsley sauce
Ingredients: 150g/5½oz potatoes, peeled and cut into 2.5cm/1in chunks; 120g/4¼oz cod fillet; 325ml/11½fl oz milk; 1 bay leaf; 1 lemon, finely grated zest of ¼ and the rest cut into wedges, to serve; 1 spring onion, trimmed and finely sliced; 25g/1oz plain flour, for dusting; 1 free-range egg, beaten; 50g/1¾oz panko breadcrumbs; 3 tbsp sunflower oil, for frying; sea salt and freshly ground black pepper; wilted spinach, to serve; 15g/½oz butter; 1 tbsp plain flour; generous handful fresh curly parsley, finely chopped; salt and freshly ground black pepper