Preheat oven to 170°C/150°C fan forced. Closely arrange the potato slices upright in rows in a 6cm deep, 19.5 x 26cm ovenproof dish.
Combine the cream and milk in a jug. Pour the milk mixture over the potato. Cover with foil. Bake for 2 hours or until the potato is tender.
Increase oven temperature to 200°C/180°C fan forced. Carefully separate the potato slices and randomly add the camembert slices in between. Bake for 15-20 minutes or until the potato is golden and cheese has melted. Top the potato bake with caramelised onion and sprinkle with thyme, to serve.
