Q. For the purpose of reheating an already cooked food in Shabbat, how dry does it have to be to be permitted? Are meat balls in their gravy permitted to warm? If yes, how much gravy can it have?
How about if when one began reheating there was little liquid but it increased considerably when warmed?
A. Mishna Berura (318: 32) mentions that as long as the liquid gravy or sauce has been removed from the item in question even if it is still moist enough to transfer wetness to something touching it, it is considered a ‘Davar Yovesh.’ (See also Igros Moshe O.H. 4: 74: 7)
Horav Shlomo Miller’s Shlit’a opinion is that if when one began reheating there was little permitted liquid but it increased considerably when warmed, it is still permitted to reheat.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.