If you fancy a more punchy, peppery flavour to the fishcakes, then use the peppered smoked mackerel fillets. They add a real punch to the recipe.
Boil the potatoes in salted water until they are cooked through, then drain and mash them with the horseradish.
Peel away the skin from the mackerel fillets and discard. Flake the fillets into the mashed potato, removing any bones if you come across any.
Add the spring onions, tarragon and season with freshly ground black pepper. You shouldn't need to add any extra salt as the mackerel is naturally salty. Gently bind everything together and shape the mixture into eight flat cakes.
Lightly dust the cakes in the seasoned flour, then dip into the egg and finally coat evenly in the 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.
Meanwhile, make the beetroot salad. Heat the olive oil in a small saucepan and then gently cook the onion for about five minutes until it has softened but not coloured.
While the onion is cooking, cut the beetroot into small cubes. Add the capers and lemon zest to the frying onions and season with salt and freshly ground black pepper.
Gently cook until the beetroot is heated through then stir in the chives.
To cook the fishcakes, heat about 1cm/0.5in of oil in a large frying pan over a low-medium heat for shallow frying. Fry the fishcakes for 3-4 minutes on each side, until they are golden, crispy and heated through. To avoid overcrowding the pan, you will probably need to do this in two batches.
Remove the cooked fishcakes from the frying pan, sit on kitchen paper to absorb any excess oil and keep warm in a low oven while you cook the rest.
Once they are all cooked and wonderfully crispy, serve straight away with the beetroot salad and a dollop of sour cream.
