Put the olive oil into a large sauté pan casserole and heat the oil over medium heat.
Add the chopped vegetables (onion, carrot, celery and garlic) into the casserole.
Stir and sweat them off until the onion become golden in colour.
Then, add the white wine, stir and let it evaporate (it probably takes a couple of minutes).
Next, add the chopped tomatoes.
Stir and cook for 5 minutes.
Then, add 1.5 litres (6 1/4 cups) of light stock and continue cooking for 15 minutes over low/medium heat.
Next, season with salt and black pepper and...
...add the fish into the casserole.
Simmer for about 15 minutes and avoid stirring because this may break the fish up.
After 15 minutes, gently remove the fish from the pan using a slotted spoon. Meanwhile keep cooking the rest of the contents in the casserole.
A bit of surgery here! Remove the main chunks from the fish, put them into a small bowl and set aside.
All the fish bone and fins go back into the casserole. Simmer for 10 minutes, then...
...pass all the casserole contents into the food mill (Mouli).
The food mill should be positioned over a second pan, usually a saucepan, which will collect all the liquid (soup). All the bones and hard bits remanining into the mill have to be discarded.
Here, we should have a lovely boneless fish soup. Meanwhile you have put the saucepan over a low heat. Check the seasoning and add salt and black pepper according to your taste.
Add the fish chunks you previously set aside. At this stage, if you want more fish, you can add some prawns or scallops.
Simmer for 5 minutes.
Add the parsley (roughly chopped flat leaf parsley).
Serve it accompanied with slices of grilled country bread.