This fruit allows the user to control seemingly limitless amounts of butter. Despite butter usually making objects slippery, the created butter has been shown to be quite sticky and adhesive when in semi-liquid form, capable of immobilizing an opponent by wrapping it around their hands or bodies.
This fruit has shown no particular weaknesses aside from the standard Devil Fruit weaknesses.
Galette uses this fruit's power in battle to immobilize and subdue her opponents, leaving them open for her allies to do as they please with them. How exactly she does this has not been shown in the manga, but in the anime she's been seen telekinetically controlling globs of butter and wrapping them around her opponent's hands and bodies.