Preheat oven to 180°C/160°C fan-forced.
Place one potato half, cut-side down, on chopping board; place a chopstick on board along each side of potato. Slice potato thinly, cutting through to chopsticks to prevent cutting
all the way through. Repeat with remaining potato halves.
Coat potatoes in combined butter and oil in medium baking dish; place, rounded-side up, in single layer. Roast 1 hour, brushing frequently with oil mixture.
Combine breadcrumbs and cheese; sprinkle over potatoes. Roast potatoes further 10 minutes or until browned.