Potato gratin topped with mozzarella

Preheat the oven to 170 degrees Celsius on the fan setting. Peel the potatoes and boil them in salted water for approx. 20 minutes. Drain the potatoes and leave to cool. Cut the potatoes into 0.5 cm thick slices. Cut the mozzarella into thin slices. Spread the potatoes out in a medium-sized ovenproof dish. Then pour the sauce over the potatoes and sprinkle with mozzarella. Bake the potato gratin in the oven at 170 degrees Celsius on the convection grill setting for approx. 35 minutes.