Thinly slice the white and green parts of the spring onion and the parsley stalks. Chop the parsley leaves, along with the mint and basil leaves, and fennel fronds (if using), and set aside for later.
In a nonstick frying pan over a medium-low heat, soften the onions and parsley stalks in the olive oil with a pinch of salt, until soft and translucent.
Meanwhile, whisk the eggs in a bowl, then add the chopped herbs, cheese and some salt and pepper, and whisk again.
Scrape the soft onion into the egg and stir, then pour back into the frying pan, put back over a low heat and cook gently until set. Lift the edge to see it is golden, then invert and cook until the other side is golden, too.