Put the grated potatoes in a bowl along with the carrots and parsnips. Mix well and season with freshly ground black pepper. Add 1 egg and half the snipped chives; mix well.
Using your hands, divide the mixture into 8 portions and form each into flattened patties.
Heat the oil in a large frying pan over a medium heat. Add the rostis and fry for 3-4 minutes on each side until crisp and golden. Meanwhile, bring a large pan of water to a simmer. Add the white wine vinegar, then crack the 4 remaining eggs into the water, one at a time. Poach for 3-4 minutes for a soft yolk, then remove with a slotted spoon.
Serve 2 rostis per person, with a poached egg on top. Garnish with the remaining chives and some black pepper.
Cook's tip: any leftover cooked veg will work in this as long as you use 400g potato as the base.