I am wondering if small portions of dough, made by separate women in a challah baking class (thus each small portion would be owned by a single woman), can be combined to create the requisite amount of dough to require blessing and separating? For example, if 10 women make individual doughs from 1/2 pounds flour, combine their doughs so that the combined dough has at least 5 pounds of flour, then bless and separate challah from the combined dough? If so, can the dough then be separated again for each woman to take her dough home to bake? This is very common at challah baking classes, and I am wondering if blessings can be said in class. Thank you so much!
The mishna (Challa 1:7) says:
נחתום שעשה שאור לחלק, חיב בחלה.
נשים שנתנו לנחתום לעשות להן שאור, אם אין בשל אחת מהן כשעור, פטורה מן החלה.
A baker who baked bread [that had the proper amount for Challah], while intending to sell pieces of it [where each piece is less than a shiur], is obligated in Challah.
Women who gave dough to the baker to make sourdough, if none of their [individual portions] has a shiur (proper amount) [for Challah], they are not required to remove Challah.
( my translation )
Bartenura there explains that the difference is that the baker, when he bakes bread, has in mind that if he doesn't find buyers for this bread, he can make it into one big loaf for himself; while the women never considered making it into one big loaf, but only that each one would take her portion at the end, and bake it herself.
Apparently, Meiri and Rashba explain this that the combined dough is viewed as separate doughs (each woman's portion by itself); while the Rash says that the obligation to separate challah only starts with a dough that will eventually become one piece.
Sources obtained from my friend SZZ -- I have not seen anything after the horizontal rule inside.