Now granted there is nothing i like better than slathering mustard on a nice fresh elfdog before i have my dragon eat it. (helps them with their spicy breath) But I seriously doubt they would get muc hmustard at the time and elves eat to maticulously to get it upon them. Hell Legolas didn't even get beer on him/her when facing Gimli and dwarves get stuff over everything. When you can not spill beer on yourself or have other people not spill stuff on you when you are drunk then there is no doubt that He would not get the mustard on himself therefore unless like someone said you had them face a mustard monster i do not believe that there would be any reason to have mustard on an elf.
That is my bit of running nothingness for the day.
P.S. No one smite me for the LOTR referrence please.
(Too late)