If you have never heard of the Valaisian specialty brisolée, do not worry. I have met Swiss people from Geneva (merely 60 km away from the canton Valais) that do not know what a brisolée is. I shall help you out!
Brisolée is a dish eaten during autumn time, when the chestnut is in prime season. It basically means roasted chestnuts with the usual Swiss suspects i.e. cheese and dried/cured meat. The cheese includes hard cheeses that come from mountain pastures but also the typical Vacherin Mont d’Or, a cheese from the Vallée de Joux in Jura, that you can only get in autumn and winter. The meats include lard, sausage, air-dried beef meat (viande séchée), ham etc. If you are missing some greenery, you often times also find new apples and grapes. Hydration-wise have some Valaisian wine (white or a light red) or some grape must, and you are good to go!
As you can see, it is an easy dish to prepare, so top-quality ingredients are key! For the chestnut preparation the best is to roast them in a special pan (with some holes on the surface) or in a brisoloir, a cylindrical metallic case where the chestnuts are rotated over a flame. Alternatively you can roast your chestnuts in a 210°C oven for 20 to 30 minutes. Before roasting, immerse the chestnuts in some water: those that stay floating on top are wormy or bad. Score the good ones with a knife in a cross form, they will peel much easier once roasted.