Lightly beat the eggs with 3 pinches of salt.
Thinly slice the spring onion and chilli (if used).
Heat the oil in a frying pan. Add the egg mixture and let it spread out evenly. On one half of the omelette add the spring onion and chilli; lay the cheese slices on the other half.
Cook over a low heat until the egg are no longer runny and the cheese is melting. Put the ham on one half then scatter the rocket on top.Turn the other half of the omelette over the ham, pressing it down slightly. Cook for a few seconds, then slide it onto a plate.
Serve warm.