1.Preheat oven to 200°C/180°C fan. Line a large oven tray with baking paper.
2.Place potatoes and sweet potato on lined tray; drizzle with oil, then season. Roast for 45 minutes, turning once, or until golden and tender.
3.Meanwhile, make dressing.
4.Heat a large non-stick frying pan over high heat; cook bacon for 3 minutes on each side or until crisp. Drain on paper towel. Coarsely chop into 5cm pieces.
5.Place all potatoes in a large bowl with kale, onion and half the dressing; toss gently to combine. Serve topped with bacon pieces and remaining dressing.
6.Combine ingredients in a small bowl; season to taste. (Makes 1⅓ cups)