For the tartar sauce, make a mayonnaise. Combine the egg yolks, oil, mustard, vinegar and some salt and black pepper in a jug and use a hand-held blender to blend. Keep the blender at the bottom of the jug and blend until the mixture has emulsified, then lift it up gently while it’s still running. Add 1-2tbsp cold water and stir to combine.
Measure out 310g of the mayonnaise into a nonmetallic bowl and add all the remaining tartar sauce ingredients. Taste, season and put in the fridge, covered, until ready to serve.
Put all the fish in a large pan, add the carrot, sliced onion, celery and peppercorns. Cover with cold water, bring to a simmer over a medium heat and poach gently for 6 minutes or until the fish gently breaks into flakes. Strain from the poaching liquid and leave to cool, then remove the skin. Put 85g of the butter and the chopped onions in a frying pan set over a low-medium heat and cook for 10 minutes until very soft.
Flake the fish into large pieces and add to the warm mashed potato, along with the onions and chopped herbs. Season with salt and pepper.
Line a baking sheet with baking paper. Divide the mixture into six portions. Shape each fishcake by packing the mixture firmly into a pastry cutter – they will be easier to shape while the fish and potato are warm. Put the fishcakes on the baking sheet, cover and transfer to the fridge until cold and firm.
Spread the flour on a plate, put the beaten eggs in a shallow bowl and put the breadcrumbs on another plate. Season each one with salt and pepper.
Preheat the oven to 200C/180C F/Gas 6. Remove the cold, firm fishcakes from the fridge. Dip each one in the seasoned flour, then the egg, then the seasoned flour again and the egg again before finally dipping into the breadcrumbs. (It’s important to do it thoroughly like this, otherwise the fish cakes could break up when being fried off.) Put them back in the fridge to get completely cold and firm.
Heat the remaining butter and enough oil for shallow-frying in a non-stick frying pan over a medium heat. Gently place the fishcakes, a few at a time, into the pan and cook for a few minutes on each side until evenly browned, basting them with the butter and oil as they gently cook.
Remove the fishcakes from the pan and transfer to the baking sheet. Bake in the oven for 10 minutes, then remove from the oven and serve with the tartar sauce.
Recipes and photography taken from The Irish Kitchen by Cherie Denham, photography by Andrew Montgomery (Montgomery Press, £30)
