Wash the potatoes, peel them and cut them into crescents. Distribute them in a buttered tray.
In another container, put 2 tbsp of butter and braise the ribs. Take them out and add them to the potatoes.
Cover the tray with aluminum foil and put it to bake in a 392°F (200°C) oven. After about half an hour, remove the foil and finish baking at 356°F (180°C).