Luxurious fish pie - any ideas please

I especially like the crispy topping bit - make it a bit more interesting.

Mishap This sounds good - forgot to say I can't put any onion in as one person allergic but it is an option in your version. A couple of idiot questions from me (I did say I am not a cook) - celeriac - grated? How much creme fraiche - a big tub perhaps and do I not have to simmer the fish a little first - probably not as you say it works fine but all the books say I should. Thank you - this sounds achievable.

I make this pie most weeks.

I buy the fish pie mix from Tesco - you will probably need 2 packs to feed 8.

Ingredients
2 x packs fish pie mix - it's yummy with salmon, cod and smoked haddock.
1 x celeriac
clove of garlic
onion if you want
creme fraiche
potatoes
bread crumbs
hard cheese - I use cheddar

OK - here we go! I use the Remoska for cooking this, but a casserole dish in the oven would do as well.

Peel and thick slice the potatoes and give them about 10 mins of boiling.
Soften the celeriac, garlic and onion in a pan (or in the Remoska)
Put them in the dish with the fish and the creme fraiche.
Season a bit - I usually add some bouillon powder and some pepper - or even tiny bits of jalapinos if you like a bit of bite.
Spread the par-boiled potato slices over the top.

Stick it all in the oven for about 30 minutes.

Whizz up the bread crumbs with the cheese to make a crispy topping and put that on top and give it a few more minutes in the oven.

Enjoy!!