In Temple times, one of the priestly gifts was a bit of dough separated before baking, called hafrashat challah.We still symbolically observe this commandment, and if your dough is big enough - more than 1.3 kilos - you remove a small amount of dough, make the blessing and burn it.
The commandment appears in Numbers (15:18-21): "When you enter the land . . from the first of your dough you shall give to the LORD." As with all first fruit Temple gifts (bikurim), hafrashat challah is about remembering that although we toiled to produce our bread, it doesn't wholly belong to us. Hafrashat challah is said to "make a blessing rest upon your home" (Ezekiel 44:30).
This mitzvah has become a time for prayer for many women, who often are (although not always) the bread bakers in the family. In Jerusalem, there are workshops in which women bake bread and pray together.
Some batmitzvah girls bake bread at their parties and lead guests in the blessing of hafrashat challah.
According to the Midrash, Sarah's dough contained a blessing, allowing it to remain fresh all week. Bread is more than a meal; it is our work and a way of connecting with loved ones.