For the celeriac remoulade: Chop off and discard the root system and peel the skin off the celeriac using a sharp knife and slicing away from yourself. Once the skin has been removed, rub the lemon rind and pulp all over the celeriac to help stop it from discolouring.
450 g celeriac, Half a lemon
Shred the celeriac, either using a mandolin, julienne peeler or a box grater, taking care to keep the shred on the thinner side, and toss the shredded celeriac in the lemon juice immediately and set aside.
In small bowl, mix together the mayonnaise, Dijon mustard, crème fraiche and parsley, and season with salt and pepper to create the remoulade sauce.
4 tablespoons mayonnaise, 2 tablespoons Dijon mustard, 2 tablespoons crème fraiche, 2 tablespoons parsley, Salt and pepper to taste
Adding a tablespoon at a time, stir the remoulade into the celeriac shreds until the dressing is coating and clinging to the celeriac, but not drowning it – think of it more like a dressing as opposed to a soup (see notes).
Set aside for at least 30 minutes for the flavours to develop and meld.
For the fish and green beans: When the celeriac remoulade has around 10 more minutes to sit before serving, prepare a bowl of ice water and a few lemon slices, and set aside. In a large saucepan, bring liberally salted water to a boil.
½ lemon
Blanch the green beans until they are tender-crisp, around 2 to 3 minutes. Immediately drain and shock in the iced water to stop them cooking any further. Drain, season with salt and set aside.
200 g green beans, Salt and pepper to taste
For the fish, heat the oil in a heavy-based frying pan over high heat. Pat the fish fillet(s) dry with a paper towel on both sides, and when the oil is hot, add the fillet skin-side down. Season with salt and pepper. If the fillet starts to curly, gently press it down using a spatula or a slotted fish turner.
1 tablespoon olive oil, 1 large fillet of firm white fish, Salt and pepper to taste
After 3 minutes, or when the skin is crisp and golden, flip the fillet and season the other side. Add the butter, basting the fillet as the butter browns, for another 2 to 3 minutes or until the fillet is just cooked through, or cooked to your liking.
50 g butter
Take the pan off the heat and squeeze the remaining lemon juice over the fish and butter to create a thin sauce. Add the parsley and right in the pan, flake the fillet apart and toss to coat in the butter, lemon and herbs.
A small handful of parsley
Serve warm over the celeriac remoulade and a side of green beans.