Mix together the courgette, garlic and thyme and fry in hot oil for 2-3 minutes.
Season with salt and ground black pepper and drain the resulting liquid.
Beat the eggs with the cream and season with salt and ground black pepper.
Add to the courgette mixture in the pan, cover and leave to solidify for 8-10 minutes.
Turn the frittata using a large plate, sprinkle with Parmesan cheese, cover and bake for a further 3-5 minutes.
Cut into squares and serve.