Wilt the chard and the onion first and squeeze the water out — a wet green turns the eggs to soup. Baked rather than fried, which is what keeps it on the gentle list; twenty minutes at 180 °C and it should still wobble slightly in the centre.
The method above is what decides the dish, not a step-by-step recipe. The link runs a web search on the name: this page has no vetted sources of its own, and will not invent any.