Heat vegetable oil in a large pot over medium heat. Add lamb shoulder chunks and brown on all sides.
Once browned, remove lamb from the pot and set aside.
In the same pot, add onions and cook until softened, about 5 minutes.
Return the lamb to the pot and add carrots, potatoes, and stock.
Add thyme sprigs, salt, and black pepper.
Bring to a boil, then reduce heat to low and simmer, covered, for about 2 hours, or until the meat is tender.
Adjust seasoning as needed and serve hot.