Add the olive oil to a large casserole or saucepan and put over medium high heat.

Meanwhile, lightly season the chicken pieces with salt and pepper.

When the oil is hot, add the chicken pieces (skin side down first) and cook until browned all over. Do this in batches if necessary and transfer the pieces to a plate when browned.

Discard all but 1 tbsp of the fat in the pan, turn the heat down to medium, and add the butter.

When melted, add the onion, celery and garlic plus a little salt and pepper. Scrape up any browned bits from the bottom of the pan and cook, stirring often, until the onion is starting to colour and soften (5-6 min).

Stir in the potato and cook for 1 min.

Return the chicken to the pan, along with any juices that have collected on the plate.

Stir in the stock and milk. Put on a lid and bring to a boil.

Turn down the heat so you have a gentle simmer and cook until the meat is very soft and almost falling off the bone (45-55 min).

Take the pan off the heat, remove the chicken pieces and leave until cool enough to handle.

Take off the meat, discarding the skin and bones.

Set aside 100-120 g of the choicest meat and roughly chop it.

Put the rest of the meat back into the pan.

Using an immersion/stick blender, whizz the soup until smooth.

The soup and the reserved chicken can be set aside in the fridge at this point if necessary and finished later.

To serve: reheat the pureed soup if necessary and add the reserved chopped chicken along with the double cream.

Simmer very gently until the chicken is warmed through.

Taste and add more seasoning if needed.

Serve sprinkled with the fresh herbs.