From the Super Mario Wiki
The Chalet Approach is an outside area of the Secret Mine in Luigi's Mansion: Dark Moon. This area is automatically accessed during Cold Case and can be entered by taking the door in the south of the Chalet. The Chalet Approach is a large area covered in snow. There are several piles of snow and leafless trees covered in snow and ice. Near the entrance to the Chalet, there are two snowmen and a sleigh with a portrait of an object that differs between missions. Luigi can peer into the Chalet via the window on the right side and there is a barbecue on the left side that can be activated with the Strobulb. Taking the north door takes Luigi to the Chalet.
During Cold Case, there is a treasure chest with money when Luigi first enters. Sucking up the snow and kicking the tree nearby causes two gold crows to fly out of the tree. The snowmen's heads can be removed and destroyed for five coins each while the sleigh on the right side has a hidden portrait of a coin that can be revealed with the Dark-Light Device. If Luigi looks into the window, he notices a Hider playing on a rocking chair. If Luigi stares long enough, the Hider violently rocks the chair, making several coins and bills pop out. The barbecue has a Gold Bar covered with ice. From Hit Rock Bottom and onwards, the Treasure Chest does not yield money anymore, but kicking the tree still causes two gold crows to fly out. The barbecue now has a rotisserie chicken on it and the sleigh has a painting of a gemstone covered with ice on it.
Starting in Hit Rock Bottom, if Luigi goes back to the Chalet Approach, there is a portrait of a sapphire on the sleigh rather than a hidden portrait of a coin. Luigi needs to remove the snow on the portrait and then shine the Dark-Light Device on the portrait to free the gemstone.