It was the Celtic invasion of Ireland that brought the cooking pot which, along with the already established spit, became the dominant cooking vessel.
For purity - both historically and conventional paleo, discount the potato; potatoes were introduced to Ireland in the Sixteenth Century.
Brown off several pieces of lamb or mutton and place into a casserole dish.
Soften some roughly chopped onion in the same frying pan and toss into the casserole dish.
Peel and quarter some potatoes. Peel and cut some carrot into similar sized chunks. Add to the casserole dish.
Chop a good bunch of parsley. Add to the casserole dish.
For purity, top up with water.
For flavour, top up with some bouillon and a couple of teaspoons of arrowroot to thicken the stew.
Bouillon is a broth made from a simmering of mirepoix, bouquet garni and some bones. You can look up mirepoix and bouquet garni but here's a cheat - you can buy powered bouillion which only needs a generous tablespoon in a litre of water. If you wanted to make up your own, it's onion, celery and carrots (the mirepoix), thyme, bay and sage tied together (the bouquet garni), some bones and water - simmer for a few hours to extract all the flavour, freeze excess as appropriate.
Bouillon can also be purchased in powdered form.
Cook for 2-3 hours in an oven set to 180C by which time the lamb should be tender.
Optionally accompany with cabbage.
Perfect for St Patrick's Day! Consume with several glasses of Guinness ... Sláinte!