- For the salted cucumber and horseradish, place the cucumber slices into a colander and sprinkle with plenty of salt. Mix well and leave the contents to drain over the sink for half an hour.
- Rinse the salt off the cucumber with cold water, then leave to drain. Gently wring out any excess moisture from the cucumber with your hands, then set aside.
- In a clean bowl, mix the horseradish with the crème fraîche and mustard powder, making sure the mustard powder is well combined with no lumps. Set aside.
- Season the mackerel fillets on their skin side with salt and freshly ground black pepper.
- Heat the butter in a frying pan until it is foaming, then add the fillets skin-side down. Place a heat-proof plate onto the cooking fillets, as this will make sure they stay flat and cook evenly. Cook for 4-5 minutes, or until nearly cooked through, then turn the fillets and cook for 30 seconds, or until just cooked through.
- To serve, place a small handful of the cucumber onto the toast. Place the cooked mackerel fillets onto the cucumber. Place a dollop of the horseradish sauce on top and garnish with a little of the sliced red onion and a squeeze of lemon.
Serves 2 - 3
- ½, cucumber peeled, thinly sliced on a mandoline
- 4 tbsp grated fresh horseradish
- 2 heaped tablespoon crème fraîche
- 2 tsp English mustard powder
- 4 fresh mackerel fillets
- salt and freshly ground black pepper
- knob of butter
- 4 slices soda bread, toasted, buttered
- 1 small red onion, thinly sliced
- ½ small lemon