Add ingredients to the slow cooker - place the chicken thighs in the slow cooker and add the onion, leek, celery, carrot, thyme sprigs and bay leaf
Rinse the pearl barley in a sieve under cold water and then add it to the slow cooker
Add the rest of the ingredients - add the crushed garlic, the salt and a good grind of pepper, then pour in the chicken stock and stir
Slow cook - put the lid on the slow cooker pot and cook on low for 6 to 8 hours, or high for 4 hours
Remove chicken and herbs - Remove the bay leaf and thyme stalks and discard. Remove the chicken pieces to a plate and shred with two forks.
Blend - using a stick blender, blend the soup for a few seconds to thicken the broth a little. You still want lots of chunky veg left so don't overdo it.
Finish - add the chicken back into the soup along with the chopped parsley and stir
Adjust the seasoning - taste the soup and add more salt and pepper if necessary before serving.