Finely shred the spring greens, discarding any really thick bits of the core. Peel and dice the onion. Dice the courgette. Peel and finely chop the garlic. Halve the chilli. Flick out the seeds and white bits for less heat. Finely chop it. Roughly chop the parsley leaves.
Warm 1 tbsp olive oil in a deep frying pan or wok. Add the onion and courgette. Season. Stir and fry for 5 mins to soften the veg.
Add the garlic and chilli to the veg. Stir and fry for 1 min till the pan smells aromatic. Add the chopped tomatoes. Quarter fill the can (around 100ml) with water and pour that in too.
Cover the pan with the lid. Bring to the boil. Turn the heat down and simmer for 5 mins till the sauce starts to thicken.
Slide the cod into the pan, skin-side down. Cover. Simmer for another 5 mins till the sauce is thick and the cod is opaque and cooked through.
While the cod cooks, pop the shredded spring greens into a pan. Cover with boiling water. Bring to the boil, then lower the heat and simmer for 2 mins till it's just cooked. Drain.
Try the tomato sauce and season to taste. Serve the cod and tomato sauce with the spring greens ribbons, sprinkled with the chopped parsley leaves.