Step 1Preheat oven to 200°C. Line a large baking tray with baking paper. Place sweet potato on prepared tray and spray with olive oil. Bake for 30 minutes, or until golden and tender.
Step 2Spray a grill pan with oil and set over high heat. Cook pineapple slices for 2 minutes on each side, or until lightly charred and heated through. Transfer to a plate.
Step 3Meanwhile, cut each chicken breast horizontally into 2 thin fillets. Place chicken on a plate. Spray fillets with olive oil, then sprinkle with Cajun seasoning.
Step 4Cook chicken on grill plate for 2–3 minutes each side, or until browned and cooked through.
Step 5Meanwhile, preheat grill. Toast rolls until light golden. Place roll bases on 4 serving plates. Top with the lettuce, cucumber, mint, chicken and pineapple. Add the tops of rolls to burgers. Serve with the sweet potato wedges.