We don't know of any fully qualified guides offering strictly backcountry tours to the area around Valle Nevado/La Parva. There are a few companies doing ski hill/off-piste trips to Chile including Valle Nevado/La Parva such as powderquest.com, casatours.com and atacpatagonia.com, while others such as alpinetouring.com do one off ski mountaineering trips to Anconcagua.