So we have a conflict. On the one hand we are supposed to cut the bread before the blessing so as not to delay between blessing and eating, but on the other hand we can’t cut the bread before the blessing, because then it won’t be whole.
what I have seen to deal with this is during the week the bread or chala is sliced but not detached the bracha is said and then cut all the way or broken off. On shabbos the sighn is made about 1/3 of the challa thebracha is made and then a slice is cut from the sighn to the middle eaten by the one who made the bracha and the cut for other members of family and geusts don’t forget first give the wife and then whoever.
the sefardim break the chala because just like no metal in the mizbaach (alter)