Heat the oil or ghee in a large heavy-bottomed pot over medium-high heat. Add the lamb pieces and brown them on all sides, about 5 minutes. Remove lamb from the pot and set aside.
In the same pot, add chopped onions. Cook, stirring occasionally, until golden brown, about 7 minutes. Add minced garlic and grated ginger; cook for 1 minute, stirring constantly.
Bring to a boil, then reduce heat, cover, and simmer for 1 1/2 to 2 hours until the lamb is tender. Stir occasionally and add water if curry gets too dry.