Boil the potatoes in salted water until they are cooked through, and then drain and mash them with the horseradish.
Peel away the skin from the mackerel and flake the fillets into the potato, removing any bones if you come across any. Add the spring onions, tarragon and season with black pepper. You shouldn’t need any salt as the mackerel is naturally salty.
Gently bind everything together and shape the mixture into 8 flat cakes.
Lightly dust the cakes in the seasoned flour, then dip into the egg and finally coat evenly in breadcrumbs.
The fish cakes are now best put in the fridge for about 30 minutes to firm up, but can be cooked straight away if necessary.
Heat about 1cm of oil in a large frying pan to shallow fry (about 1 cm deep) over a low-medium heat. Fry the fishcakes for 3-4 minutes each side, until they are golden, crispy and heated through. You will most likely have to do this in a couple of batches.
Remove the cooked cakes from the frying pan, sit on kitchen paper to absorb any excess oil and keep warm while you cook the rest.
Once they are all cooked and wonderfully crispy, serve straight away with the beetroot salsa and a dollop of sour cream.
For the Beetroot Salsa:
Heat the olive oil in a small saucepan and then gently cook the onion for about 5 minutes until it has softened but not coloured.
While the onion is cooking, cut the beetroot into approximately 5mm cubes. Add to the onions with the capers and lemon zest. Season with salt and pepper and gently cook until the beetroot is heated through. Stir in the chives and serve warm with the fishcakes and sour cream.
This warm salsa is the perfect accompaniment to the fishcakes.
To speed things up, I make the most of the freshly cooked beetroot sold in the salad section of supermarkets, rather than boiling and peeling your own.
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