I mean, a new abjuration food/drink that gives, say, HP+150, MP+150, Refresh+10, Regen+10, ACC, ATT, RACC, RATT, DEF +15% (Cap 150), MAC+50, MEVA +50, MDB+15, MAB +15, lasts 6 hours, and most importantly, cannot be dispelled, and possibly lasts through death, would not be out of line for, say, a 110 recipe that requires Cursed Soup, in addition to a rare/ex abjuration which is a guarranteed drop from CL135 Escha/Reisenjima NMs would not be out of line, I think, given that other Abjuration 119 gear is BiS or, if not BiS, pretty damn good, compared to all other items in the game.

Give it a synergy version (still yields one) that allows people who aren't cooks to find a cook who can make one (giving money to both the cook and the synergist helping make it), and you might have something that makes cooking worthwhile.

The cost involved in mats and skill and difficulty of getting the abjuration would make it something that would sell well, requiring the NM victories would make the content something people would still do for the food, and the fact that it IS so hard to get/expensive to get/hard to make would mean that other foods would still remain viable and desirable alternatives.