Melt the butter in a small ovenproof frying pan over a medium heat. Add the eggs, stir gently and then leave to settle.
Sprinkle over one teaspoon of chives, parsley and the horseradish. Cook for two minutes and then fold over one half onto itself and cook for another minute, until golden underneath.
To serve, place the omelette onto a small plate, sprinkle with the remaining teaspoon of chopped chives and place the rocket on the side.