Beautiful route that can be done in one day taking the first cablecar of Grand Montets (3.223m). It's possible also comig up from the village of Argentière when the cablecar is closed. In this case it is advisable to divide the route in two days sleeping at the Refuge d'Argentière (2.771m). It is useless to leave the refuge too early. In case of good snow conditions, it is possible to use the ski untill the last 100 meters, but however axe and crompons are required (better 2 axes).
From the top of the Grand Montets cablecar station, descend on the Glacier des Rognons following the trail to a height of 3.100m. Take the slope just right. Continue down the glacier avoiding the crevasses, towards the spot elevations 2.754m (Rognons morraine). There isn't a precise direction, it depends to the snow conditions of the year. However try to reach the flat part of the glacier on the safer way. The crevasses are many. In case of a fast route, do not ski in the direction to the refuge, but point to the Glacier de Milieu.
Go up the glacier, staying on its right bank up to 3.350m approximately. Crossing and reach the left side under "The Casque" to go up towards the bergschrund that exceeds passing on the right bank of the glacier. The slope is now quite steep (35° to 40° PD/S3) and steeper gradually up to a couloir where it becomes narrower (45°/50° AD/S4). The base of the couloir is usually the ski depot. The slope gradually softens until the summit ridge located between the west and the top main peak (ice warning!). If good skier, bring the ski until the top. Descend the same route up to the Argentiere glacier. Cross it and reach the left bank. Follow this side and go under the moraine Rognons. Towards the 2.550 meters, a crack in the glacier creates a zone of cracks more or less difficult depending on the year. Stay on the extreme left of the glacier to overcome it. Follow the glacier up to 2300 meters and then leave it and reach the ski resort of Argentiere. Good luck..