May one mix mayonnaise with tuna or eggs on Shabbos?

Some[1] rule it is forbidden to be made on Shabbos.[2] Others[3] rule it may be done on Shabbos.[4] [Practically, one may do so using an irregularity.[5] Thus he is to first place in the mayonnaise and then the tuna/eggs, as well as he is to mix it [using his fingers or by shaking the bowl, and if this is not possible then he may] with a spoon back and forth and opposed to in a circular motion. It is preferable to remove the spoon between each time. The above only refers to mixing mayonnaise with small pieces of egg or tuna and hence making it into a single lump. However, if the piece of the egg or tuna are chunky, and hence do not form a single lump, it is permitted to be mixed according to all, even without an irregularity.]

May one mix mayonnaise into eggplant to make Chatzilim?

This follows same status as egg salad in which some Poskim[6] prohibit making it on Shabbos, while others[7] rule it is permitted. [Practically, it is best to only do so before Shabbos.[8]]

______________________________________________________________________

[1] Shabbos Kehalacha 22:70

[2] The reason: As it is forbidden to make a thick batter on Shabbos due to the kneading prohibition.

[3] Nishmas Shabbos 321:305; Orchos Shabbos 6:18 footnote 46; Shabbos Kehalacha 7:61; So I saw ruled in the name of Rav Shternbuch

[4] The reason: As from their understanding, there is no prohibition of mixing mayonaise with a solid on Shabbos even in accordance to Rebbe Yehuda, and therefore, since the mixture is Eino Bar Gibul, it does not transgress the laws of kneading at all. [See Shabbos Kehalacha ibid]

[5] The reason: Although a thick mixture is made, since this is un-kneadable material [which according to the first opinion may always be made with an irregularity] and the food is cooked, and had water placed in it before Shabbos through the cooking, therefore even according to the opinion of Rebbe Yehuda, there is no kneading prohibition involved. This certainly applies with tuna that was in a can in which it actually sat in liquid, and hence whether according to Rebbe Yehuda, or Rebbe Yossi, it is permitted to be kneaded, as according to Rebbe Yehuda it was already pre-kneeded, and according to Rebbe Yossi it is Eino Bar Gibul which may always be kneaded with an irregularity. [See Admur 324:3]

[6] Shabbos Kehalacha 22:70

[7] Nishmas Shabbos 321:305; Orchos Shabbos 6:18 footnote 46

[8] The reason: As we are initially stringent like the opinion who holds it is forbidden to knead even Eino Bar Gibbul, and here there is no added Heter of it being pre-kneaded, as it is not cooked in other liquids.