Place the stock in a large saucepan and bring to a simmer. Add the diced lamb and simmer gently for 25-30 minutes, skimming any scum that comes to the surface. Add all the other ingredients to the pan apart from the pearl barley and simmer for 25 minutes, continuing to skim any scum off the surface as necessary.
Remove the lamb at this point and add the pearl barley to the broth. Simmer for 30 minutes or until the pearl barley is tender and soft. Add the lamb back to the broth and allow it to reheat until hot. Season to taste, then stir in the chopped parsley. Ladle into soup bowls and serve immediately.
Freezing and defrosting guidelines
Make the soup, then leave to cool at room temperature. Freeze (without garnishes or toppings) in a rigid container, leaving a bit of space for expansion, for up to 1-3 months. Reheat either from frozen or defrost in the fridge overnight. Once piping hot, add toppings or garnishes and serve.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.