Hilchot Shabbat - Hatmana (wrapping/insulation) of food

Tzurba M'Rabanan Volume 18 in English - Hilchot Shabbat - Hot plates, adding hot water to food and time switches - Shiur 5.  Shiur given at Kehilat Mevaser Zion, Tel Mond by Rabbi Darren Platzky on 19 January 2025