Butter

Butter was a spread made from milk, particularly the fat it contained. As a child, Amy Pond served the Eleventh Doctor bread and butter. He didn't like it and threw it away, saying, "And stay out!" (TV: The Eleventh Hour)

The Tenth Doctor helped Layla make butter. (AUDIO: Dead Air)

Tibetans made tea with yak butter in it to fortify them from the cold. (COMIC:Yonder... The Yeti)