Heat the vegetable oil in a Dutch oven over medium heat. Add the lamb chunks and brown them on all sides for about 6 minutes. Remove the lamb and set it aside.
Add the diced onion to the same pot and cook for 4 minutes until softened. Stir in the minced garlic and Madras curry powder and cook for 1 minute until fragrant.
Return the lamb to the pot. Pour in the diced tomatoes with their juices and the broth. Add the salt and black pepper. Bring the mixture to a simmer.
Cover the pot and transfer it to a 325°F oven. Braise for 1 hour and 30 minutes.
Remove the pot from the oven. Stir in the carrots, potatoes, and parsnip. Cover and return to the oven for another 45 minutes until the vegetables are tender and the lamb is soft.
Taste and adjust salt if needed. Sprinkle with chopped fresh cilantro before serving.