Written by Rabbis Eli Gersten, Yaakov Luban, and Moshe Zywica of the Orthodox Union
When should the preparation of the shank bone, charoset, horseradish, roasted egg, salt water, and checking the romaine lettuce take place?
Seder preparations should be done on Friday, as it is prohibited to prepare on Shabbat for the next day. (This is known as hachanah. One may not even nap on Shabbat and say, “I am resting now to be alert at the Seder.” See Mishna Berurah 290:4.) While it would be permitted to prepare some of these items on Saturday night, this would delay the start of the Seder and it is important to start the Seder as soon as possible before the children fall asleep, as much of the Seder focuses on them (M.B. 482:1).
According to the Vilna Gaon, horseradish should always be grated immediately before the Seder so that it will be sharp. Others say it should be grated before Shabbat and stored in a sealed jar to maintain the sharpness as much as possible. If one forgot to prepare horseradish before Shabbat, the grating should preferably be done with a shinui (deviation, such as grating on a paper towel or turning the grater upside down).
Romaine lettuce that requires checking for infestation should be checked before Shabbat. One must be careful to drain the lettuce very well, otherwise, water might accumulate in the bags, and any parts of the lettuce that soaks in water for more than 24 hours may not be used for marror (M.B. 473:38).
If salt water was not prepared in advance, it can made on Yom Tov (implication of M.B. 473:21), though some recommend using a shinui by putting the water in the vessel before the salt (Kitzur Shulchan Aruch 118:4).
If charoset was not made before Shabbat, the fruit may be grated on Yom Tov, but the nuts should be prepared with a shinui, such as crushing in a bag (Shemirat Shabbat K’hilchatah 7:4). No deviation is needed when adding the wine (see M.B. 495:8).
It is preferable to roast the shank bone and egg before Shabbat. If roasted on Yom Tov, they must be eaten on that day of Yom Tov. Since one may not eat roasted meat or chicken at the Seder, the shank bone or egg that were prepared Saturday night must be eaten at the Sunday daytime meal (M.B. 473:32). In general, one may not prepare food on the first day of Yom Tov if the intention is to consume it on the second day or after Yom Tov. (This would constitute hachanah, which is forbidden.) As such, another shank bone and egg will have to be roasted Sunday night for the second Seder, and the same is true for the preparation of marror, charoset and salt water.