From the mid-station of the Aiguille du Midi cable car (Plan d'Aiguille), follow signs for the Lac Bleu and start skinning eastward and under the Aiguille du Plan and the Blatière. Cross over several small moraine walls (might require a couple of very short boot packs) and head towards the Nantillons Glacier. Drop over one final short but steep moraine wall and onto the Nantillons Glacier. Skin up a little further until under the first rock wall you come to a steepening. Transition to boot packing and climb up a brief steep and rocky section often involving very faceted snow (tiring boot packing). The angle decreases before steepening again up to 45 degree in a small couloir. After the couloir it is normally possible to transition back to skinning before reaching another steeper (sometimes icy) slope. Then reach a small flat area which marks the entrance to the Spencer Couloir. The couloir is sustained at 45 degree before steepening to 50 at the top. Ski back down the same way, or it is possible to exit the upper section of the Nantillons Glacier skier's right. Ski back to the mid station or back to town if snow cover allows.