From the parking follow the ski du fond track up onto a high point with a little chapel. As the road drops head south to a small bridge, cross it and follow the track to the Chalets du Buffère (a great place to grab a drink on the way down).  From there follow the GR 57 south aiming for the Pointe de Buffère.

Here you have two options:  1) Going via the north near the Lac de Prive and then climbing from the north to the col at the back of the pointe du Buffère and then traversing in to the couloir (this is a slightly longer way and there are some steep slopes to traverse but is stunning popping over the col) 2) stay on the GR57 and then turn after the Pointe du Buffère and climb direct to the couloir. This option is shorter (not by that much) and gives you the chance to see the whole line you will ski.

Descent

Ski down the couloir and then head north east, keeping some height to ski back to the chalets and refuge for a well-earned drink. From there follow the track down - its a tight, steep descent and not easy if icy, but it is possible to ski in the trees at the side of the path to make it easier. That said, stick near to the path as there are big drops around. From the bridge a small walk leads you back to the ski du fond track and then down to the parking.