Not sure if you're talking about the chocolate souffle from Palo, or one of the other souffles from a menu served in the Main Dining Rooms, but - the 3 nights of the cruise that each dining room is serving it's "own" menu, it's generally possible to get something from one of the "other" menus served to you if you ask early in the service. That's because those items are already being prepared for their respective dining rooms.
On any other night, when all dining rooms are serving the same menu, then it's quite unlikely that you can get something from a different menu, as those items are not being prepared that night.
But, as noted, requesting the chocolate souffle from Palo in the Main Dining Rooms is a "no go". Unless, possibly, you are Concierge.