Above-average manual dexterity
Since most of the deaf speak sign language WP
and since sign language relies heavily on hands as the primary vehicle of expression, it is likely that the deaf develop above-average manual dexterity, which would sure come handy in many cooking tasks (say, chopping or cutting)
Since they have one less sense to distract them, they can focus more on flavors. The blind are known to have very refined senses of hearing and smelling, perhaps something similar happens to the deaf?
No stress in noisy environments
Kitchens can be pretty hectic environments, right?
Clear, quick note-writing ((and reading)
It is likely that they have had to rely many times on writing clear, quick notes to strangers so they might have developed systems or experience for making them easily understood. That may come in handy in busy kitchens were a lot of information is passed on written notes (so that, say, orders don’t get all mixed up).
Different food cues
They may have discovered different cues for food quality or meal readiness (say, since they can’t hear milk burbling, they might smell when milk is just about to boil over).
Sign language is a noiseless language
So it might be better at restaurants where absolutely no noise is desired from the kitchen. (On the other hand, perhaps it’s hard for a deaf person to accurately assess just how much noise they inadvertently make with cooking instruments.)
More accurate people-reading
A deaf may have learned to rely more on other people’s body language and thus may be more accurate gauging whether people honestly liked her dishes or not.