Preheat the oven to 180°C/350°F (160°C fan).
Heat a large, ovenproof skillet on high heat, add the olive oil and cook the lamb shanks for 6-8 minutes until browned, turning regularly. Set aside and turn the heat off.
Add the massaman paste, coconut milk, beef stock, potatoes and red onions to the pan. Stir to combine and return the lamb shanks to the pan (or transfer to a baking dish if needed).
Cover tightly with a lid or two layers of foil. Bake for 2 hours or until the lamb is soft enough to be shredded with a fork.
Sprinkle with chilli and coriander to serve (if using).
Serve with lime wedges, jasmine rice and naan bread.
