Finely chop the shallots, garlic, celery, carrot, and red pepper.
Heat the olive oil in a large casserole or saucepan and gently cook the vegetables for about 8 minutes, until softened.
Add the balsamic vinegar and let it bubble for a moment to deglaze the pan.
Stir in the thyme and tomato purée, mixing well to coat everything.
Add the chopped tomatoes, chicken stock, and bay leaf.
Add the halved potatoes and bring to a boil, then reduce the heat and simmer for about 20 minutes, until the potatoes are just tender.
Stir in the lamb and chickpeas. If the stew feels too thick, add a little more stock.
Add the olives and green vegetables, and cook for another 5 minutes until everything is heated through and the greens are cooked.
Taste and adjust seasoning if needed.
Ladle into large bowls and finish with chopped parsley.
Serve with a crisp green salad on the side.