To make the sweet potato chips, preheat the oven to 200°C (fan 180°C/gas mark 6). Cut the large sweet potato into chips and toss them with the coconut oil. Season with salt and pepper. Roast the oven for 12-25 minutes until lightly browned.
Meanwhile, place the chicken, ginger, garlic, chili, coriander, zest and juice and breadcrumbs into a food processor. Season and blitz until well blended. Preheat the grill to medium. Shape the mixture into a large patty and place under the grill for 5-6 minutes on each side, or until cooked through and lightly golden.
To serve, spread the yoghurt on the base half of the toasted brioche bun. Top with the lettuce, tomato and cucumber ribbons. Place the burger on top, spread over the mango chutney and top with the toasted bun lid. Serve with the sweet potato chips.