From the bottom of the snow arete from the Aiguille du Midi cable car head along the broad snowy ridge towards the Aiguille du Plan. There is a 100m section where you have to sidestep/walk up and after this the ridge steepens on both sides. You normally ski on the right hand side of the ridge to a platform above a steep bowl that faces east with a ridge heading down to your right and some steep cliffs in front of you. This is the start of the route proper. From here the skiing takes the furthest possible left-hand line by hugging the cliffs for almost all the way via some steeper pitches and a short couloir. After several kilometers you will join back up with the Vallee Blanche route which you can follow down the glacier to Montenvers/the track back to Chamonix.
This is a true classic which can be heaven or hell. You need to know where to go since there are crevasses on many places. It starts steep, gets flat amd them there is a new steeper section before the last womderful 500 m down to mer du glace.