The Rama (Rabbi Moshe Isserles of Cracow, Poland, 1525-1572), in Orah Haim (242), records a custom to eat on Shabbat a type of food called "Muliyata," or "Pashtida," which is dough filled with a stuffing of meat or other food, what we would call sambusak. The reason for this custom, the Rama explains, is to commemorate the manna which fell from the heavens to feed Beneh Yisrael during their travels through the desert. This food consists of meat covered with dough on top and on bottom, resembling the manna which was covered by a layer of dew on top and another layer on the bottom. The Be'ur Halacha (Rav Yisrael Meir Kagan of Radin, 1839-1933) raised the question of why we commemorate the manna specifically on Shabbat – the one day during the week when manna did not fall from the heavens. Why would there be a custom to eat a type of food that resembles the manna on the one day when the manna did not fall? One answer that is given is that specifically because there was no manna on this day, it is necessary to make a commemoration to celebrate this miracle. However, the Be'ur Halacha cites a different answer from a work entitled Torat Haim, an explanation which he describes as a "Ta'am Hagun" ("proper explanation"). He writes that Shabbat represents the "Yom She'kulo Shabbat" – the next world, Olam Ha'ba, which will be a perfect world, kind of like an everlasting Shabbat. The Shabbat we observe each week is a kind of window into the next world, a glimpse of the delights and serenity of Olam Ha'ba, and for this reason we observe several customs that bring to mind the future world. Thus, for example, we eat meat and fish, commemorating the meat of the "Shor Ha'bar" animal and of the "Livyatan" fish which will be fed to the righteous in the next world. Likewise, we make Kiddush on wine to commemorate the special wine that G-d has prepared already at the time of creation to give to the righteous in Olam Ha'ba. The commemoration of the manna may similarly be seen in this light. Our Sages teach that there is a section of the heavens called "Shehakim," which comes from the verb "Sh.h.k." – "grind." It is so named, we are taught, because manna is ground in that section of the heavens, and is prepared to be fed to the Sadikim in the next world. Accordingly, it is possible that we eat food symbolizing manna not to commemorate the manna eaten by our ancestors in the desert, but rather to commemorate the manna that will be fed to the righteous in the future. On Shabbat, when we are given a glimpse into the everlasting Shabbat of the next world, we eat food resembling the manna that will be fed to those deserving of basking in the glory and enjoying the delights of the "Yom She'kulo Shabbat."