Light a lidded barbecue. Let the flames die down and the coals turn ashen, then mound the coal up on one side or heat an oven to 180C/160C fan/gas 4. Arrange the sweet potatoes on a large tray and drizzle with 1 tbsp of the vegetable oil, season and toss. Cook on the barbecue or in the oven for 25 mins until charred and softened.
Meanwhile, whisk the remaining oils, ginger, garlic, soy and lime juice. Baste the potatoes with some of the sauce and return to the barbecue for another 30-40 mins, basting as they cook. Once the potatoes are glazed and sticky, remove and sprinkle on the sesame seeds and peanuts, and leave to cool slightly. Remove the wedges from the tray and pop into a salad bowl. Sprinkle over the chilli and spring onions and serve.