Thinly slice the onion and bell peppers. Heat the oil in a large, non-stick frying pan and gently soften the garlic, onion and pepper, stirring occasionally. It should take about 10 minutes.
Add the beans and chilli flakes (if used), followed by the chopped parsley. Cook for a couple of minutes.
Meanwhile, lightly whisk the eggs with a fork.
Pour the egg mixture over the vegetables, letting it spread out evenly. Cook over low heat for about 10 minutes. When the top of the omelette is gooey, brown it quickly under a grill.
Serve warm.