Chocolate
From Tardis Wiki, the free Doctor Who reference
Chocolate was a food made from cocoa, perhaps most notably enjoyed by humans. Because it was naturally bitter, it was often sweetened with sugar.
The Torchwood Pteranodon liked dark chocolate, which was the only thing he would eat without barbecue sauce. (TW: Fragments)
The Tenth Doctor and Martha Jones traveled the universe in search of the perfect chocolate milkshake. (IDW: Doctor Who #1) Later, he enjoyed a chocolate Easter egg, but then passed it to Lady Christina de Souza after becoming concerned that its sugar content might harm his teeth. (DW: Planet of the Dead)
On Colony 34, outside the walls of third city, chocolate was one of the many items that was very hard to get a hold of. (BFA: Live 34)
