To make the dressing, mix the sweet chilli sauce, lime juice, and 1 tbsp of the sesame oil in a bowl, stirring to combine.
Take 1tbsp of the dressing mixture and put it in a separate bowl, then add the fish sauce, remaining sesame oil, half the coriander, the garlic, and the pork, and toss so the meat is well coated.
Preheat the grill. In a serving bowl, mix the cucumber, mango, onion, and remaining coriander. Grill the pork for 2-3 minutes on each side, until cooked through. Dress and season the salad, and serve with the pork, along with some rice, if you like.