Challah: The Braided Bread for Shabbat
There is one piece of every challah that nobody eats. The baker tears it off the raw dough, a piece the size of an olive, wraps it up and burns it. That piece is the real challah: the word doesn't originally mean the bread at all, but the tax on dough that the Israelites owed the priests. The whole loaf is named after the part that is missing from it.
Challah (Hebrew: חלה) is a braided yeast bread of flour, eggs, oil and sugar that Israeli cooking and the whole Jewish diaspora put on the table on Friday night and on holidays - just not at Passover, when leavened dough isn't allowed in the house.

The Tax on Dough That Gave the Bread Its Name
The command is in the Book of Numbers: separate a portion from your dough and give it to the priests. As long as the Temple in Jerusalem stood, the priests ate it; once it was gone, the piece could no longer be eaten in ritual purity, so it is burned or wrapped up and thrown out. Everyday speech then turned the name of the tax into the name of the bread, and the name stuck. The braid itself has nothing to do with the Torah - it took hold only in medieval Central Europe, most likely following the ceremonial loaves of Christian neighbors, and the word challah is first written down in this sense in an Austrian manuscript from 1488. So this is an Ashkenazi bread: Sephardic families traditionally left the dough unbraided and scattered seeds over it, and Yemenite and Ethiopian Jews have a completely different bread for Shabbat. In Polish cooking the chałka caught on so widely that people who have never kept Shabbat in their lives buy it, and in America the bread grew bigger and sweeter as sugar and eggs got cheap there. In today's Israel every community bakes it. An Ashkenazi custom turned into a national bread.
Why There Is No Butter in Challah
Challah looks like a sweet braid from any European bakery, but you won't find butter in it. Traditional challah is parve, made without milk or butter so that it can be eaten with the meat meal waiting on the table on Friday night; that is why oil keeps the dough soft and the shine comes from an egg wash rather than milk. The rabbis banned milk bread outright so that nobody would serve it with meat by mistake, and allowed a single exception: for Shavuot you may bake a buttery one, but in a conspicuously different shape so that it can't be mistaken for the ordinary loaf. Raisins go into the dough, sesame or poppy seeds onto the crust - by tradition a reminder of the manna in the desert.
Two Loaves, a Cloth and a Blessing
Two loaves belong on the Shabbat table. The rule of lechem mishneh is a reminder that a double portion of manna fell in the desert on Friday, because on Saturday none fell at all. Both loaves lie covered with a cloth until the blessing is said over them, and only then are they torn or sliced - that order is never reversed. For Rosh Hashanah, the Jewish New Year, challah isn't braided but coiled into a circle, because the year is not supposed to have an end, and it is brushed with honey so the year will be sweet. Anyone who wants bread from the oven rather than off the shelf goes to the bakery on Thursday or on Friday morning: some Jerusalem bakeries open on those two days only, and every one of them closes on Friday before sunset. So on Saturday you don't buy challah, you finish it.
A Small Loaf for Three Shekels in Jerusalem
I bought my challah in Jerusalem, in a Friday bakery where the loaves lay in wooden crates; I took the smallest one they had. The crust was glossy, sesame fell off it with every bite, the braid pulled apart in soft threads and the crumb stayed soft even with no butter in it. Next to the sweet braided loaf we bake back home for Christmas it is a moister and less sweet bread, something to eat with a meal rather than with tea or coffee. The small loaf cost 3 ILS (0.80 EUR). The baker had given up his piece that morning, into the oven. I handed over three shekels, and I don't think either of us lost out on the deal.