In the cake bedroom, take the musical angel that is playing the mandolin, which should be setting to the right of the cake bed, move it to the center of the mantel of the fire place.  Then move the sleeping lion, sitting behind the pillows on the bed, to exactly where the angel was sitting to the right of the bed. 

Look where you took the Lion from.

The shelf below where the Lion was sitting should open.  If it doesn't clear the pillows out of the way and rearrange the Lion in the spot where the Angel used to sit until the shelf opens.