Dust lamb shanks in flour, shake off excess flour, and season all over. Heat oil in a large ovenproof stockpot or saucepan with a lid over high heat. Sear lamb, turning frequently, for 4-5 minutes, until browned all over. Remove from pot and set aside.

Preheat oven to 160°C/140°C fan-forced.

Add whole eschalots, garlic, carrot, celery, and herbs to the pot, drizzling in a little extra oil if needed. Reduce heat to medium and cook, stirring occasionally, for 2-3 minutes, until fragrant.

Return lamb to the pot, increase heat to high, and add wine, scraping the base of the pan with a spoon. Cook for 1-2 minutes, until evaporated. Add stock, barley, and enough water to cover lamb by 5cm. Bring to the boil, skimming any impurities that rise to the surface. Braise, covered, in the oven for 2 hours 30 minutes to 3 hours, until meat falls off the bone.

Remove pot from oven and transfer lamb to a large heatproof bowl. Set aside to serve the meat on the bone, or when shanks are cool enough to handle, shred meat from bones, discarding bones.

Place pot over high heat and return to the boil. Skim any fat and impurities that rise to the surface. Season to taste and add a little extra stock or water if the soup is too thick. Return meat to soup and stir to combine.

To serve, divide soup among bowls, scatter with lemon zest and parsley, and drizzle with extra oil.