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.
2Combine butter and half the pesto, spread over one side of each piece of toast. Top with roasted sweet potato and mozzarella. Place under hot grill until light golden.
3Drizzle with remaining pesto, sprinkle with basil leaves. Serve.