From the Dôme des Rousses, access Lac Blanc.
You can take the gondola up to Dôme des Rousses, but if you're feeling sporty, you can also walk! Once you've reached Dôme des Rousses, head down the slope in front of you. Follow it all the way down to Lac Blanc. You can then take the DMC 2 gondola back to Poutran.