Bring a large pan of lightly salted water to the boil and cook the potato cubes for 15 minutes until just tender. Drain well. Meanwhile heat the oil in a 30cm/12inch heavy based frying pan and cook the onions over a moderate heat for 5-8 minutes until soft and golden. Add the well drained potatoes and cook over a high heat for 5 minutes, stirring well, until the potatoes brown a little in places, not worrying if they break up a little.
Add the chopped chives and season well with salt and freshly ground black pepper, and toss well. Spread the potatoes evenly throughout the pan then spoon small spoonfuls of the soured cream between the potatoes, until all is used.
Beat the eggs well and pour over the potatoes to cover. Cook over a moderate heat for 5 minutes, whilst preheating the grill to hot. Transfer to the grill and cook for 4-5 minutes until the top is golden and set. Cut into wedges to serve.
If serving vulnerable groups, elderly people, toddlers, pregnant women and people who are unwell, cook eggs until the whites and yolks are solid.