1Preheat oven 200°C fan forced. Slice sweet potato into 1cm-thick rounds. Place into a roasting pan. Drizzle with olive oil, season, turn to coat. Roast 30 minutes, turning once until golden and tender.
2Spread butter over one side of each piece of toast. Top with roasted sweet potato. Sprinkle with feta, olives then top with tomato. Sprinkle over half the parmesan. Place under hot grill until light golden. Sprinkle with remaining parmesan. Serve.