Eruv Tavshilin - Cooking on Yom Tov for Shabbat.

Normally, it is forbidden to prepare food on Yom Tov for use the next day. However, when Yom Tov falls out on Friday, one may prepare for Shabbat on Yom Tov if he began the preparations before Yom Tov. This preparation is known as an Eiruv Tavshilin. 

On erev Yom Tov one sets aside two types of food, one cooked and one baked. If one cannot obtain both items, a cooked item alone would be acceptable but a baked item alone would not suffice. The cooked item must be at least the size of a large olive and the baked item should be at least the size of a chicken's egg.

The selected food are held in one's hands while the Bracha and subsequent Aramaic text, as they appear in the Siddur, is recited. It is necessary to understand the meaning as it is recited. If one does not understand it, it should be recited in one's native language (Rama 527:12).

The Eruv Tavshilin allows one to prepare for Shabbos only on Erev Shabbos, but not on the first day of Yom Tov (Shulchan Aruch 527:13). In addition, every effort must be made to complete the preparations early enough on Friday afternoon so that the food will be edible well before Shabbos. Nevertheless, if the preparations were left until late Friday afternoon, they may still be done (Beiur Halacha 527:1).

The food items used for the Eruv Tavshilin must remain intact as long as preparations are being made for Shabbos. Perishable items used for the Eruv should be stored in the refrigerator as needed. If the Eruv foods were consumed or discarded, the Eruv ceases to be valid (OC 527:15). 

If a challah (or matzah) is used as the baked item of the Eruv, it is customary to use the challah for additional mitzvos as one of the two loaves of lechem mishnah at each of the three Shabbos meals, and to consume the challah at the third meal of Shalosh Seudos.

Click here for printed text of Eruv Tavshilin.