Wash the potatoes, using a toothrush to clean their skin. Afterwards, boil the potatoes in hot water.
Take a little saucepan, melt the butter at low heat and add 1 clove of crushed garlic along with some leaves of sage.
Place the peeled potatoes in a baking tray and pour the flavoured butter on them. Also cover the potatoes with the Emmental slices.
Put the potatoes in a pre-heated oven (it should be very hot) with the grill function for a few minutes. When the potatoes are golden, remove them from the oven and serve them with rosemary.