Requiem Shard

Exceptional dishes when bought separately will automatically stack in the character's pack, but when you unstack them they will revert to standard quality and thus lose the bonus uses. In order to prevent this, one alternative would be dropping to the ground each dish before buying another of the same kind and then keeping them separated.

The dish in question was a sweet cake.

If this was mine, I'm afraid the only suggestion I have is to get a separate food container and manually drag each item into the open container. It seems to be a UO stacking thing.