Warm 1 tbsp olive oil in a medium pan. Add the lamb. Fry over a medium heat for 5-8 mins till the lamb is browned all over. Turn it once or twice to make sure it browns evenly.
While the lamb fries, peel and dice the onion and carrot. Trim and finely slice the celery. Pick the leaves off the parsley sprigs. Put them to one side. Finely chop the stalks.
Add the onion, carrot and celery to the pan. Season with salt and pepper. Cook over a lowish heat for 5 mins, stirring now and then. The veg should start to look soft and glossy.
Crumble the stock cube into a heatproof jug. Pour in 800 ml boiling water. Stir to dissolve the stock cube. Stir the parsley stalks into the veg with the pearl barley.
Pour in the chicken stock. Turn the heat up and bring the stew to the boil. When it’s boiling, pop on the lid. Turn the heat down. Simmer for 30 mins.
While the stew simmers, halve the squash. Scoop out the seeds and peel it. Chop the squash into smallish chunks. Add them to the pan. Simmer for 8-10 mins till the squash, lamb and pearl barley are tender.
Finely chop the parsley leaves. Stir them into the stew. Taste and adjust the seasoning. Ladle into warm bowls to serve.