Place the grated potatoes in a clean dry tea towel and squeeze out the excess liquid, transfer to a large bowl and mix in the flour and half the spring onions, season well. divide into 6 and shape into flat patties.
Heat 1 tbsp oil in a frying pan and fry 3 rosti for 3-4 minutes each side until golden, repeat with the remaining rosti. Meanwhile, poach the eggs in boiling water for 2-3 minutes.
Divide the rosti between 2 plates, add the smoked salmon and top with an egg. Sprinkle with remaining spring onions and chives to serve.