The eiruv tavshilin must be prepared before the festival begins. One holds a baked food such as bread together with a cooked dish, such as fish, meat, or even a boiled egg, and recites the blessing:

“Blessed are You, Lord our God, King of the universe, who sanctified us through His mitzvot, and commanded us concerning the mitzva of eiruv.”

Then one recites the following paragraph, which can be said in any language one understands:

“By this eiruv we shall be permitted to bake, cook, insulate food, light a flame, and do all that we require on the festival for the sake of Shabbat, for us and for all Jews living in this city.”

One sets aside the baked item and the cooked food to be eaten at one of the Shabbat meals. They should be put in a safe place to ensure that they will not be eaten before Shabbat.

Important clarification: When a festival falls on Saturday night there is no way to cook on Shabbat in honor of the festival, not even by means of an eiruv tavshilin. Not only may one not cook on Shabbat, but all preparation from Shabbat to the festival is prohibited, as the sanctity of Shabbat is greater than that of the festival. It is permitted to cook the festival food on the festival itself.