Depending on cut of lamb, leave it on the bone or cube it if boneless - a mix is best.
Put into a large pot and cover with stock (the above quantities are very rough). Add onion and celery.
Simmer for about 2 hours.
Season VERY generously.
Meanwhile, peel and slice potatoes and soak in a bowl of cold water for about 1 hour to reduce the starch.
Add gradually to the lamb, along with the carrots, still seasoning generously.
Stir frequently over about 1 1/2 hours, keep adding potato slices until the stew is thickened to a paste.
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