Yesterday, I noticed on my Jewish community email group that someone was sponsoring a group challah "bake off" for refu'ah shleima (speedy recovery) for a group of ill people.
I have seen these announcements frequently. I am unfamiliar with this custom. How does baking challah provide a blessing for the ill? When did this custom originate? Is this effective only in a group setting, or can an individual baking challah have the same effect?