In my opinion mashed celeriac is greatly underrated. It is so much lighter than mashed potato and the flavour is delightful. This fish pie freezes well and is almost as tasty when reheated, so I usually make a double portion when I cook it.
Peal the celeriac and clean up the messy root side, the cut up in inch sized cubes. Put them in a saucepan and cover with milk, bring to the boil and let simmer until the celeriac is soft. It takes some 15-20 minutes. Then fish out the celeriac cubes and mash them with a food blender or by hand. If you need some extra moisture, add a little of the milk. Season with dried powdered ginger and nutmeg.
I like to have different kinds of fish in my pie. The combination of salmon, cod and prawns is one favourite, but you can add whatever you like. Estimate 100-150 grams of fish per portion in total.
Cut up the fish in bite sized bits and drizzle a mix of lemon and lime juice, freshly squeezed, over. Mix with a generous amount of finely chopped fresh dill and the zest from the citrus. Stir in crème fraiche to make a nice mess.
Butter an oven-proof dish and line it with the mash. Pour in the “fish mess” in the middle. If you want to be naughty you can sprinkle some grated cheese on top, which gives the pie a crispy crust and a little extra flavour.
Cook in the oven at 200C until golden brown, 30-40 minutes.