1 tsp mustard
1 tsp salt
1 tbsp white wine vinegar
225 ml olive oil
2 tbsp fresh dill, chopped, plus extra to garnish
1 medium sweet potato, peeled and grated
Salt and black pepper
3 tbsp ghee or coconut oil
1 cucumber, peeled into long strips
1 a red onion, thinly sliced
150 g smoked salmon, sliced into strips
Juice of 1/2 a lemon
1 For the mayonnaise, put the egg yolks in a bowl with the mustard, salt and white wine vinegar. Drip the oil onto the egg yolks extremely slowly, drop by drop, whisking at the same time.
2 When the mixture begins to thicken, add the oil a little faster, in a slow, steady stream. Stir in the dill, then taste and add more seasoning and/or vinegar if necessary.
3 In a bowl, mix the sweet potato with the egg and add half a teaspoon each of salt and black pepper.
4 Melt two tablespoons of ghee or coconut oil in a pan over a medium-high heat. Transfer the potato mixture to the middle of the pan. Use a spatula to spread the mixture out until just under a centimetre in thickness.
5 Turn the heat down to medium and cook, covered, for 2-3 minutes. To flip the rösti, put a large plate face down on top of the pancake and turn the pan upside down so the rösti falls onto the plate. Melt the remaining ghee or oil in the pan and slide the rösti back in. Cook, uncovered, on a low heat for three minutes, then turn the heat back to medium and cook for a further 2-3 minutes.
6 Carefully transfer the rösti to a large serving plate. Spread with the dill mayonnaise and pile with the cucumber strips, onion and smoked salmon. Squeeze over some lemon juice, season with black pepper and garnish with extra dill.