We are not permitted to prepare food on Yom Tov for the next day, even for Shabbat. However, when Yom Tov falls on Friday, it is permitted to prepare food needed for Shabbat if we make an Eruv Tavshilin before the holiday, indicating that the preparations were started before Yom Tov.  We take two ounces of matzah and one ounce of cooked food (egg, fish or meat) and set them aside on Erev Yom Tov, and they are to be eaten on Shabbat. The foods used for the Eruv Tavshilin are held in the person’s hand and the following is recited.