Heat 2 tbs olive oil in a dutch oven over medium heat.
Add lamb and sear each side for 1-2 minutes until browned. Remove from pan.
Add onion, carrot and celery and cook for 3-5 mins until soft. Add a dash more olive oil if it's sticking.
Add garlic, and fennel and cook a further 3 minutes.
Stir through harissa paste if using.
Add tomatoes and chicken stock. Bring to a simmer.
Once simmering, add in the pearl barley. Bring to the boil then reduce heat.
Return the lamb shank meat back to the dutch oven.
Cover, simmer over low heat for 1 hour 30 minutes - 2 hours, or until soup is thick. Lamb should be falling off the bone, or easily shredded with a fork.
Remove lamb from soup with a slotted spoon and use two forks to shred the shanks. Place back into cast iron.
To serve, stir through the lemon juice.
Spoon into bowl, then top with greek yogurt (optional), mint or parsley, extra lemon zest and pomegranate.