Preheat the grill. Heat a non-stick frying pan with a splash of olive oil and a knob of butter.
Cook the chopped onion with a little bacon for 3-4 minutes or until lightly golden. Add leftover chopped potato or sweet potato and cook until lightly golden.
Whisk the eggs together with the cream or crème fraiche, pour over the potatoes and crumble over feta cheese or grated Cheddar.
Cook over the heat until the egg begins to set. Finish it off under a hot grill until the centre is set. Serve warm with a green salad.