One of the ways we repair the damage caused by the sin of Adam and Chava is to separate a portion of the dough when we make bread. When the Beis HaMikdash is standing, this portion is given to the Kohen (priest). The question is: why does Hashem entrust this task specifically to women?
Some basics on how this is done today:
1) Challah is separated from a dough made from the “five types of grain” (wheat, barley, spelt, oats, rye) if more than 1.2 kg. (2.64 pounds) of flour is used.
2) According to the Chazon Ish, Challah is separated with a blessing only if the dough was made from a minimum of 2.25 kg (4.95 pounds) of flour.
3) It is forbidden to separate Challah on Shabbos.
4) After the dough is kneaded but before it’s formed into loaves, one first recites the blessing (asher k’dishanu … v’tzivanu l’hafrish Challah) and then separates a portion about the size of an egg (no matter how big the batch of dough is).
5) The separated portion is burned until it’s inedible, wrapped twice, and discarded.
In Likutey Halakhos, Yoreh Deah 2, Hilkhos Challah 2:4-5, Rav Nasan of Nemirov brings the teachings of Rabbi Nachman to reveal some of the profound secrets informing this mitzvah. Speaker: Rabbi Nasan Maimon.