1. Blot the grated potato with kitchen paper to remove excess water. Place in a bowl and mix in the onion granules, salt, pepper, egg yolk and flour.
2. Heat half the oil in a large frying pan. Use a tablespoon measure to spoon 8 piles of the potato mix into the pan. Flatten each into a 6cm cake and cook gently for about 15 minutes, turning, until cooked through. Drain. Repeat with remaining oil and potato mixture to make 16 cakes in total.
3. To serve, leave to cool for a few minutes whilst cutting each salmon slice into 8 short strips. Top the warm rösti with soft cheese, salmon and chives. Alternatively, leave the rösti to cool completely and serve cold.
