Preheat oven to 230°C. Line a large baking tray with a layer of non-stick baking paper.
Cut potatoes and sweet potato into 1.5cm-thick wedges. Place potatoes in a large oven bag with water, adjusting until they are 2-3 deep when the bag is laid flat. Twist the opening to close.
Place the bag directly on the microwave turntable and cook on High/ 800watts/100% for 7-8 minutes or until firm but tender.
Use scissors to snip one corner of the bag and drain. Carefully untwist the bag, and spread potatoes on the lined tray in a single layer. Spray potatoes with olive oil spray to lightly coat.
Roast in preheated oven for 15 minutes or until lightly browned. Turn the potatoes and spray with olive oil to lightly coat. Roast for a further 15-20 minutes or until tender and crisp.
Meanwhile, to make the sweet chilli yoghurt, combine the yoghurt and sweet chilli sauce in a small bowl. Taste and season with salt and pepper.
Season wedges with salt and pepper and serve immediately with the sweet chilli yoghurt.
Serving size: 6
Recipe courtesy of taste.com.au