Heat oil in a large heavy based pan, and fry cutlets for a couple of minutes on each side to brown. Remove the cutlets, discard the oil and add the stock to the pan. Bring to a boil, stirring and scraping the bottom of the pan, and then add the rest of the stock.
Place half of the onions in a large ovenproof casserole dish. Top with one third of the butternut squash, then add half the carrots and celery, and all the sage and thyme and cutlets. Season with salt and pepper, and then sprinkle the barley over the vegetables. Repeat the layering and top with remaining butternut squash. Pour the stock over everything and cover with a lid or aluminium foil.
Cook in the preheated oven for 1 1/2 hours or until the lamb is tender, checking occasionally and adding more stock if needed. Remove the lid and increase the temperature a little. Cook for 8 to 10 minutes, until potatoes have browned.
I think I've cooked this stew about 5 times now, big hit with the family. I'd prefer the sauce to be a bit thicker, but no-one else seems to mind. I don't use cutlets, just the packets of stewing lamb you can buy in the supermarket. I never put in potatoes as they were not in the ingredient list, but its just as good served with couscous! - 05 Sep 2009