From the Super Mario Wiki
The Luiginary Ice is the sixth Luiginary Work seen in Mario & Luigi: Dream Team. It allows Dreamy Luigi to heat up or freeze an area. It is activated and used by Starlow by grabbing Luigi's left hand on the touch screen to press a button.
Freezing the area freezes water and bouncy platforms, allowing Mario to push the platforms to different places. Heating up the area thaws water and bouncy platforms, allowing Mario to bounce on them. This Luiginary Work is based upon the Airway from Mario & Luigi: Bowser's Inside Story.