Preheat the oven to 180 Fan/160c conventional.
Add a drizzle of oil to a medium sized oven-proof non-stick frying pan (approx. 25cm) and set over a medium heat. Add the zucchini, season well with salt and pepper, and fry for about 5 minutes, stirring often, until softened and starting to turn golden.
Add the red onion and fry for about 10 minutes, stirring, or until softened.
Add the garlic and fry for 30 seconds, stirring, until fragrant.
Sprinkle over the cheese and the chives, then pour over the eggs and cook over a low heat for about 4 minutes, shaking the pan gently and moving it around to get an even cook (at this point,, the bottom of the frittata will be cooked but the top won't).
Pop in the oven for about 4 minutes - or until puffed up and almost firm to the touch. Watch closely as you don’t want it to overcook and become rubbery.
Remove the frittata from the oven and slide onto a chopping board.
Top with parmesan shavings, feta and the parsley and red onion salad.
Cut into slices and serve.