1. Mango chutney Heat the oil in a medium saucepan and add the onion, ginger and lemongrass. Cook for 5 minutes or until the onion is browned lightly – stir occasionally. Add the remaining ingredients and bring to the boil. Reduce the heat and simmer, uncovered, for 15 minutes. Transfer to a 500ml glass jar.
2. Pork fillet Finely chop the roots and stems of the coriander and put into a bowl with the oil, chilli flakes, hoisin sauce and vinegar. Stir to combine. Add the pork and toss to coat in the marinade. Marinate for 30 minutes or overnight.
3. Heat a grill plate or large frying pan over medium-high heat. Cook the pork for 5-10 minutes on each side or until done as desired. Transfer to a warm plate and rest, covered loosely, for 5 minutes.