the family is at the shabbos meal, and the pot of stew or meat is sitting on the hot plate or covered stove. it gets lifted off to serve a portion, and the rest needs to go back on the heat because people at the table will probably want seconds.

the ohr yitzchak (siman 73) explains that chazara is forbidden not because anything will actually cook. the food is fully cooked, there is no bishul achar bishul, and on a covered stove there are no coals to stoke. the reason is mechzi k’mevashel, it looks like cooking, the ran and the rashba on shabbos 38b, brought by the mishna berura on siman 253. the shulchan aruch (oc 253:2) gives the working conditions: the kira is gerufa uktuma, the food is still boiling, the pot stayed in his hand, it was not put down on the ground, and he meant to return it from the start.

1. when the pot is taken off just to serve and the plan from the start is to put it right back, what exactly are the conditions? does he have to keep holding it the whole time, or is setting it on the counter for a moment already a problem? does the food have to still be hot, and how hot?

2. if the whole reason is how it looks and not real cooking, does it matter where it goes back, a hot plate or covered stove versus an open flame? and does it matter how long it sat off the heat?

3. and if the pot never leaves the heat at all, it stays on the hot plate for the whole meal and only the ladle goes back and forth, is that plainly fine, or does serving straight from the fire have its own issue?

bottom line: with a normal hot plate or covered stove today, what are the working rules for serving from the pot at the meal and putting the rest back on the heat?