Mustard
From Memory Alpha, the free Star Trek reference
Mustard is a Human condiment made primarily from the ground seeds of the mustard plant.
Sisko's Creole Kitchen offered shrimp remoulade: gulf prawns with a dipping sauce of mustard, capers, shallots, and onions, as a special in 2372. (DS9: "Paradise Lost"
When Jadzia Dax and Worf briefly canceled their wedding in 2374, Miles O'Brien ordered a double Altair sandwich, with no mustard. (DS9: "You Are Cordially Invited")
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Another never mentioned, the Klingons apparently make mustard, at least according to Penny Juday and the Star Trek: Deep Space Nine art department. Juday shows the container in the DS9 Season 1 DVD special feature "Secrets of Quark's Bar".
