In a large pot, heat the dripping over medium high heat. Add the onion, parsnip, carrot, leek and garlic. Saute the veg until soft and slightly coloured, then remove from the pot and set aside.
Add the lamb to the pot and brown evenly on all sides. Once the lamb has taken some colour, drain some of the fat from the pot (as little or as much as you'd like!) and then return the veg to the pot. Add the potatoes and cover with water. Bring to the boil, then cover and reduce to a simmer. Simmer for 2 hours.