Instruction

• step 1 Heat oven to 160C/140C fan/gas 3
• Heat 1 tbsp oil in a heavy-bottomed casserole, season the shanks, then brown them 2 at a time on all sides, adding the remaining oil for the second batch
• Remove the lamb and add the onions
• Fry them quite briskly, about 30 secs, add the ginger, garlic and chopped chilli, then turn the heat down and cook for 1 min
• Add 1 tbsp sugar, stir, then add the star anise, lemongrass, stock, purée and seasoning
• Bring to the boil
• step 2 Cover and cook in the oven for 1½ hrs, then add the sweet potatoes and cook for 1 hr more
• The lamb should be completely tender and almost falling off the bones
• Stir in the fish sauce, lime juice and 1 tsp sugar to just lift the flavour, then scatter with the mint, basil and the sliced chilli to serve