01 - Generously season the lamb pieces with salt and freshly ground black pepper.
02 - In a large, heavy-bottomed pot or Dutch oven, heat the oil or butter over medium-high heat. Brown the seasoned lamb in batches until seared on all sides, then remove and set aside.
03 - Add the chopped onions, sliced carrots, sliced parsnips, and sliced celery to the same pot. Sauté for approximately 5 minutes, ensuring to scrape up any browned bits from the bottom.
04 - Stir in the minced garlic and cook for 1 minute until fragrant.
05 - Return the browned lamb to the pot. Add the potato chunks, bay leaves, thyme sprigs, beef or lamb stock, and water. Bring the mixture to a gentle boil, then reduce the heat to low.
06 - Cover the pot and simmer for 1.5 to 2 hours, stirring occasionally, until the lamb is very tender and the vegetables are cooked through.
07 - Remove the bay leaves and thyme sprigs. Taste and adjust the seasoning with additional salt and pepper as needed.
08 - Ladle the hot stew into individual bowls, garnish with the chopped fresh parsley, and serve immediately.