Cocoa, also known as hot chocolate, was a beverage made from chocolate.
In 1454 Mexico, the First Doctor drank cocoa with Cameca, which in Aztec culture meant that the two of them were engaged to be married. (TV: "The Bride of Sacrifice")
In the 1970s, Mike Yates planned to use the Bunsen burner in the Third Doctor's laboratory to heat some cocoa. (TV: Terror of the Autons)
Evelyn Smythe loved cocoa so much that she insisted upon bringing her own supply of cocoa mix on her initial trip in the TARDIS. She shared some with William Leaf and George Crow, but Crow didn't like it, preferring ale. (AUDIO: The Marian Conspiracy) After she witnessed the death of Cassie Schofield, the Sixth Doctor offered Evelyn some chocolate cake and cocoa to help her feel better; it did not help. (AUDIO: Project: Lazarus)
The Tenth Doctor and Rose Tyler had hot chocolate during their visit to Paris. (COMIC: A Date to Remember)
When the Seventh Doctor was unfrozen by the crew of the Rochester in 2012 Antarctica after millions of years, he was given cocoa. He couldn't get enough of it. (AUDIO: Frozen Time)
The Brigadier kept Benton's recipe for cocoa on hand after he retired. (PROSE: Downtime)