Crack the eggs into a bowl and whisk until smooth.
Grate the courgette and add it to the eggs along with a pinch or two of salt. Mix well.
Heat a little olive oil in a frying pan over medium heat. Pour in the egg mixture and tilt the pan so it spreads evenly.
Slice the olives into rings and scatter them over the surface.
Crumble the sardines and distribute them evenly across the pan.
Cook for a few minutes until the edges are set and the centre is still slightly wobbly.
Sprinkle your chosen cheese over the top.
Cover with a lid and cook until the frittata is set and the cheese has melted.
Alternatively, place the pan under a grill for a golden, lightly caramelised top.
Finish with a scattering of chopped parsley, chilly flakes and ground pepper, then serve warm.