Peel the potatoes and cut them into 1-inch pieces.

Heat the olive oil in a flameproof casserole, preferably terra-cotta, then add the sage leaves and unpeeled garlic clove. Sauté very lightly for 2 minutes, then add the potato pieces and stir with a wooden spoon. Cover and cook for 2 minutes over low heat, then stir the potatoes again. Season with salt and cover the casserole again. The potatoes should be stirred about every 2 minutes, but must be kept covered in between. After 20 minutes, they should be cooked.

Remove the clove of garlic and transfer the potatoes to a serving dish. Serve immediately, sprinkling with freshly ground pepper.