Fish pie

750g cod, halibut, or other white fish, filleted

250g smoked haddock or other smoked fish

500ml milk

1 small onion, roughly chopped

bay leaf

100g butter

30g plain flour

1.5kg potatoes, peeled and quartered

2 tbsp single milk or cream

salt

black pepper

225g cooked peeled prawns

1 tbsp capers in brine, drained, rinsed, and chopped

2 tbsp parsley leaves, chopped

15g Parmesan, grated