I adore fish pie....and you can add anything you want to it if you like it.
I always have a white fish, a smoked fish, some prawns, some whole mussels, maybe some cockles....lots of different flavours and textures (fish are poached in milk and the milk used for the sauce).
Then i add some chopped onions, sweetcorn and peas, chopped peppers and sliced mushrooms. Bit of shopped parsley goes in with Hollandaise or just a basic cheese sauce with mash on top. Grated cheese and dried thyme top the pie off !!!
delicious but seems to take ages to prepare (but worth it) and costs a fortune !!!!