The poskim disagree whether one may make a thick mixture on Shabbat using a shinui when the food is intended to be eaten on Shabbat. Some forbid this, arguing that the Sages permitted kneading with a shinui only in the case of a loose mixture, where the prohibition is only rabbinic. In contrast, a thick mixture may not be made even using a shinui, as it involves a Torah prohibition (Rambam). Others maintain that in order to make food for Shabbat, even thick mixtures may be made with a shinui (Tosafot).
In practice, at a time of need, when it is a case of great necessity, one may rely on those who are lenient and prepare a thick mixture using a shinui. For example, when the only readily available baby food was a thick porridge prepared by adding water or milk to a dry mix of oatmeal or other grain, it was permitted to prepare this porridge with a shinui. Similarly, in times when there was no food available for animals other than a thick mixture of bran and water, it was permitted to make such a mixture with a shinui.
The shinui is relevant both to the order in which the ingredients are added and to the manner of stirring. If there is a set order for the ingredients, it should be reversed. If there is no set order, the dry ingredients should be added first, followed by the wet ingredients. As for the manner of stirring, the spoon may be moved back and forth in a straight line or perpendicularly rather than with a circular motion. If this is not recognizable as a shinui, the spoon should be completely removed from the mixture after each stirring motion.
However, in practice, it is very rare for a leniency to be necessary here, since as a general rule there is no pressing need to prepare a thick mixture on Shabbat. Nevertheless, the lenient opinion is very important, because there are cases in which it is unclear whether a specific type of mixture would be prohibited because of Lash. In such cases, one can follow the lenient opinion and knead with a shinui. It is preferable to do so for fairly immediate consumption (when Rashba is lenient).
In cases where practically all poskim agree that Lash applies to a particular type of mixture, one may not form it even with a shinui. For example, one may not mix sesame seeds or nuts with honey. Similarly, one may not mix butter, cocoa, and sugar together, since they form a thick mixture. Such mixtures are prohibited even if done with a shinui and for immediate consumption.
. In Shabbat 156a we find that R. Yossi Be-Rabbi Yehuda permits making a thick dough of mursan (coarse bran) using a shinui. The law is dependent on two issues:
- a) Whom we follow in the disagreement between R. Yehuda Ha-Nasi and R. Yossi Be-Rabbi Yehuda (mentioned above in n. 5). If the halakha follows R. Yehuda Ha-Nasi, then the act of joining the two ingredients is forbidden by Torah law. If this is the case, then changing the order in which the ingredients are combined is not enough to permit an action that is otherwise prohibited by Torah law (Terumat Ha-deshen53). However, if the halakha follows R. Yossi Be-Rabbi Yehuda, then the joining of the materials is only prohibited rabbinically (and according to Tosafot it is permitted), so changing the order is a sufficient shinui.
- b) Whether the Sages permit making thick dough using a shinui. According to Rambam and those who agree with him, mursan is incapable of forming a proper dough, so mixing it is only prohibited rabbinically. Accordingly, the entire permission granted by R. Yossi Be-Rabbi Yehuda is limited to rabbinically prohibited kneading. (This is also the opinion of Rid and Ritva. SA quotes Rambam.) On the other hand, many Rishonim feel that mursan can be made into dough and doing so is thus prohibited by Torah law. Accordingly, R. Yossi Be-Rabbi Yehuda permits this kind of kneading with a shinui. (This disagreement is summarized in BHL 324:3 s.v. “ein.”) In times of necessity, one may be lenient. This is because according to most poskim, the halakha regarding adding water follows R. Yossi Be-Rabbi Yehuda; since even those who are stringent agree that mixing with a shinui is only a rabbinic prohibition, the halakha follows those who are lenient. It can also be inferred from Taz and BHL that most poskim are lenient.
. One can be lenient if a shinui is used, as long as there is also a substantive doubt about whether Lash applies to the mixture under consideration. However, if only a small number of authorities maintain there is no prohibition of Lash, their opinion is not enough to allow forming a thick mixture, even with a shinui. Let us mention two lenient positions that should not be taken into account since only a few authorities follow them:
- a) It would seem that Rashba 4:75 allows forming a thick mixture for immediate consumption, and a few Aĥaronim take this position into account in ruling leniently (see Livyat Ĥen67). On the other hand, many did not accept Rashba’s position, and some maintain that even Rashba was stringent in this case. Alternatively, it is possible that Rashba is lenient only when the mixing is done in the course of eating. This means that two foods on one’s plate may be mixed together and consumed (even then it is doubtful whether one may be lenient; see SSK ch. 8 n. 10).
- b) Some maintain that just as Toĥen pertains only to produce but not to meat and eggs, so too Lash applies only to produce (Maharshak; see Tzitz Eliezer 11:36). However, according to the majority of poskim, Lash does apply to other things besides produce, as Igrot Moshe states in OĤ 4:74, Lash8.