In a heavy based pot heat up 2-3 tablespoon of olive oil, add the onion, carrot and celery and fry on a medium heat for about 5 minutes. Next add the garlic and chilli into the vegetable mix.
Carry on frying, stirring occasionally until the onion turns translucent and soft.
Pour in the stock, tomato passata and stir in the saffron. On a gentle heat bring the soup to the boil and add the previously cooked chickpeas as well as the orange zest (if using) and a few pinches of smoked paprika. Give it a stir, put the lid on and let the soup gently bubble away for about 20 minutes until all ingredients turn lovely soft and tender.
In the meantime wash the clams under cold running water.
Put them into a separate small pan, cover with a lid and put on a medium heat.
Once you notice that the clams begin to open under the heat pour in a good splash of white wine. Shake the pot, put the lid back on and keep on cooking until all the clams have opened. Immediately take the pot off the heat and allow to cool down for a few minutes without the lid.
Set a strainer over a bowl and pour over the released cooking liquids and clams. Once the clams have drained pour the white wine and clam juices into the boiling soup (be careful not to pour any residues of sand which have settled on the bottom of the bowl).
Peel the clams, discard the shells and keep covered until needed.
Wash very well the spinach leaves and wilt them on a hot pan, drizzle with olive oil and season with a pinch of salt. Alternatively you can cook the leaves in a small quantity of salted boiling water for a couple of minutes.
Taste the soup, season with salt and more smoked paprika to your liking. Discard the orange zests.
Finally ddd the prawns into the soup and cook everything together without the lid until the prawns start to curl and are cooked through, which should take just a few minutes or so.
Next stir in the clams along with the cooked spinach leaves. check the seasoning again and serve immediately, preferably with a lovely crunchy bread on the side.