It is a widespread custom to eat a mixture of eggs and onion at the Shabbos table. Many prepare the mixture at the Shabbos table, even though this touches upon a number of halachic considerations: cutting the onion too small; mixing the eggs and onion with oil, resembling lash, kneading. The Klausenberger Rebbe, zl, was once asked to give his approbation to a lengthy dvar Torah that discusses the halachic ramifications. He refused, claiming it would make him guilty of meharher achar Rabbo, questioning the ruling of his Rebbe. Apparently, all his ancestors insisted on preparing the eggs and onion mixture at the table – he was not to question or even deliberate their practice.
We eat eggs and onions on Shabbos for a variety of reasons, some of them esoteric and beyond the scope of this paper. One of the popular reasons is: eating onions reminds us of the manna that descended in the Midbar. It had the taste of just about any type of food that one wanted to taste – except for a few foods. One of those was the batzeil, onion. Since v’karasa l’Shabbos oneg, it is a command to call Shabbos a delight, we want to have all types of delicacies at the Shabbos table. Moshe Rabbeinu was niftar, passed away, on Shabbos. Since eggs are a food eaten by mourners, we potentially honor his memory by eating eggs. Eating an onion alludes to having our Shabbos expenses repaid – batzeil, onion – batzalin, repay. Hashem reimburses our Shabbos expenses. Last, egg and onion are two foods that, once peeled, should not be left overnight. Thus, these two foods are, by their very halachic adherence, an indication that they had been prepared specifically for this Shabbos.
