Is there a halachically correct way to mix mashed eggs, oil and cut onions on Shabbos or Yom Tov?
Preparing egg salad is a question that many poskim have discussed.
At first glance, there would appear to be a problem in mixing together the eggs with onions and oil, because this causes the mixture to stick together, which might be a violation of lash–kneading.
However, Rav Shlomo Zalman Auerbach pointed out that the common custom was always to prepare egg salad on Shabbos, and offered a number of reasons why this might be permitted:
1. The eggs are cooked, and according to the Biur Halachah there is no prohibition of lash on cooked items.
2. The onions and the oil (that are not cooked) only serve as a “spice” for the eggs, and therefore this is considered preparation of food, and not an act of kneading.
3. The intention is not to prepare one block of food, but only to mix the onions and oil with the eggs, and to enhance their taste.
4. Some maintain that mashed eggs are not similar to flour (tiny particles that stick together) (see Eishel Avraham 321).
5. Egg salad would go bad if prepared earlier, and therefore the ordinary custom is to prepare the egg salad close to the meal, indicating that this is only an act of eating, rather than an act of kneading.
Because these reasons are not entirely convincing, Rav Shlomo Zalman recommended that the egg should be mixed with the oil and onions with two shinuyim, changes from the ordinary method of preparation. One shinuy is to add the egg to the oil, rather than the oil to the egg; another shinuy is mixing the mixture in a criss-cross pattern, rather than a circular motion (mixing slowly might also be sufficient).
After making the salad, one should preferably not smooth it out to make it look nicer (Shevet Halevi 1:86, writing especially of salads with potato; see, however, Cheshev Ha-Efod 2:77, who writes that for egg and onion alone there is less concern).
See Shemiras Shabbos Kehilchasa p. 83-84; Shulchan Shlomo p. 453. See also Mishnah Berurah 321:68 (concerning making the two shinuyim). According to Minchas Yitzchak (9:28), each one of the people at the table should make his own “egg salad” by mixing in the oil and onions (with the shinuying mentioned).
Rav Shlomo Zalman, and other poskim (see Ha-Elef Lecha Shlomo, Orach Chaim 139; Be’er Moshe 6:44), stress that the custom was always to prepare egg salad in the regular manner, and this custom cannot be brushed aside.
Some suggest that there is no prohibition of lash with regard to items that do not grow from the ground, but this rationale is deferred by Iggros Moshe (Orach Chaim 4:74).