Lamb shanks are cut from the leg of the lamb and tend to be a tougher cut of meat. It is best slow-cooked for longer periods of time to help break down the meat. It will become melt in your mouth good as this is one of my all-time favorite dishes.
Set the lamb to the side and add the prepared vegetables to the pot and continue to cook over medium-high heat until they are well browned, which takes about 10 minutes.
Stir in some tomato paste until it is completely mixed in. This will help thicken it. If the high heat is concerning you at this point, turn it down to medium.