Heat the oil in a large, heavy-based frying pan. Season the eggs with salt and pepper, then pour into the pan and cook over a gentle heat for 4–5 minutes until the base is set and the top is almost set.
Meanwhile, beat the soft cheese in a bowl with the measurement water until very soft.
Spoon the cheese over the omelette and gently spread a little. Arrange the smoked salmon over the top, then scatter over the chives and cook gently for a further 1 minute until the top is warm.
Fold one side of the omelette over the other. Serve cut into 4 wedges, with a simple salad, if liked.