As we stated in section 7, a kli rishon can cook anything, a kli sheni can cook only kalei ha-bishul, and a kli shlishi cannot cook at all. However, the poskim disagree regarding the status of a davar gush (hot, solid food).
Some maintain that the general rules of vessels apply in this case as well, and once a davar gush is moved to a kli shlishi it cannot cook anything that is placed upon it. This is the opinion of the majority of poskim (Rema; Vilna Gaon; Pri Megadim; Ĥatam Sofer; Nishmat Adam).
However, some poskim are stringent and rule that the aforementioned principles apply only to liquids or soft foods that come into complete contact with the walls of a pot. Such foods can no longer cook if they are transferred from a kli rishon to a kli sheni and from a kli sheni to a kli shlishi. But chunks of solid food – pieces of meat, kugel, potatoes, or clumpy rice – retain their heat even when transferred from vessel to vessel, as the walls of the new vessels do not have a strong cooling effect on solid food. Therefore, as long as these foods remain at a temperature of yad soledet bo or hotter, they are able to cook, no matter how many vessel transfers they have undergone (MA; MB 318:45).
In practice, since this relates to a Torah prohibition, it is appropriate to be stringent. However, if one is in doubt about whether cooking would be involved, one may be lenient even le-khatĥila. Therefore, if one can touch the piece of food and it is doubtful whether it is yad soledet bo, there is no need to worry that it will cook (see section 4 above). Even if it is clear that it is still yad soledet bo, one may put previously-cooked cold gravy on it, since some maintain that ein bishul aĥar bishul applies to liquids as well (see section 5 above). Similarly, one may salt the food, since salt can only be cooked in a kli rishon that is on the fire (MB 318:71). Additionally, one may place pickles or raw vegetables on a hot piece of kugel or meat, because one does not intend to cook them.
In contrast, one may not sprinkle raw spices like paprika and pepper on a hot piece of meat or kugel, as there is a benefit to the spices cooking – it enables their taste to be absorbed more effectively into the food. Therefore, before adding spices to a hot dish, one should wait until it has cooled off enough that one can touch it.