From Darthipedia, the Star Wars Humor Wiki, currently editing over 582,970,995 articles
Delicious, evil cookies. They are made of pure evil, hence why they are so delicious
- "Come to the dark side...we have cookies!"
- ―Darth Vader on cookies
A cookie was a desert favored by the Sith. They would offer the Jedi cookies in exchange for going over to the dark side.
It is believed that this led to Luke Skywalker's fall to the dark side, as everyone knew he couldn't resist sweets.
Asajj Ventress offered Ahsoka Tano a cookie once. She declined... and got PWNed in a lightsaber fight.