Put the lamb onion and carrot through the grinder or chop in food processor. Mix in a bowl with the gravy or stock. Put tomatoes in boiling water and leave to stand for a few minutes then remove skins chop and add to the mixture. If using canned tomatoes drain off liquid chop up tomatoes and add to the mixture. Add rice and herbs and season with salt and pepper to taste.
Scrub squash well.
Cut in half lengthwise remove seeds and fill both halves with stuffing. Place side by side in pan with about half an inch of water in it. Cover it with foil and bake at 400 degrees for one hour. Remove from oven,take off foil, sprinkle grated cheese over squash and return to oven for a further ten minutes. Cover with cold water, bring to the boil and simmer for three hours.