I've had enough of these bland DDD-s. Everyone knows that you can't have a proper hot dog without sauerkraut and mustard. So, I'd like to see all sorts of condiments in the game - sauerkraut, pickles, lettuce, mustard, mayonnaise, ajvar and more.
How would condiments work? Well, I think it'd make sense if they were combined with the main food item to raise it's quality by about 1/10 of the condiment's quality. This would be useful for when you have food that is just a couple of quality points short of giving more FEP.
Of course, some limit on condiments is needed. You shouldn't be able to use the same condiment twice on one food item. Also, it might be a good idea to limit what condiments can go with which food, so you can't improve your carrot cake by coating it in mayonnaise. Then again, people eat even weirder combinations all the time, so it'd be rather hard to decide what goes with what.
Finally, improving food with condiments shouldn't be limited by the cooking skill. Anyone with an IQ in at least double digits knows how to put mayonnaise in his sandwich.