- 500g/1lb 2oz new potatoes, cooked in their skins
- 2 tbsp olive oil
- sea salt and freshly ground black pepper
- 2 shallots, finely sliced
- 2 tbsp soured cream
- 2 tbsp creamed horseradish
- 2 tbsp finely chopped fresh chives
- olive oil
- watercress leaves, to serve
- 8 mackerel fillets
- 100g/4oz butter, softened to room temperature
- 1 tsp cayenne pepper
- 2 tsp sweet smoked paprika
- 1 tsp ground coriander
- 1 tbsp golden caster sugar
- ½ tsp English mustard
- few drops Tabasco
- 2 tsp red wine vinegar
- sea salt and freshly ground black pepper
- For the horseradish potatoes, bring a large pan of salted water to the boil and boil the potatoes, in their skins, for 10-15 minutes, or until tender. Drain and, when cool enough to handle, cut into quarters.
- Heat the olive oil in a large frying pan over a medium heat, then add the potatoes and season, to taste, with sea salt and freshly ground black pepper. Fry the potatoes for 7-8 minutes, turning occasionally, until crisp and golden-brown. Remove the fried potatoes from the pan and set aside to drain on kitchen paper.
- Meanwhile, for the spiced mackerel, preheat the grill to its highest setting. Score the skin of each mackerel three times on each side using a sharp knife.
- Preheat the grill to high.
- Mix all of the remaining spiced mackerel ingredients together in a bowl to form a thick, spiced butter and season well with sea salt and freshly ground black pepper. Rub the butter over the mackerel fillets, then grill for 4-5 minutes, turning once, or until just cooked through.
- To finish the horseradish potatoes, transfer them to a mixing bowl. Stir in the shallots, soured cream and creamed horseradish and season, to taste, with salt and freshly ground black pepper. Stir in the chives.
- As soon as the mackerel are cooked, transfer to serving plates and spoon the horseradish potatoes alongside.