The Shulchan Aruch (168:10) addresses the issue of "Chabitza," or pieces of bread soaked in soup, with respect to the laws of Berachot. Does bread in soup retain its status as bread, and thus require the Beracha of "Ha'motzi Lechem Min Ha'aretz" and Birkat Ha'mazon, or does it lose this status and require instead "Borei Minei Mezonot" and "Al Ha'michya"?
The Shulchan Aruch distinguishes in this regard between pieces of bread that amount to a Ke'zayit – thirty grams, or approximately half a pita – and smaller pieces. He rules (listen to audio for precise citation) that if one places in his soup pieces of bread that are a Ke'zayit or larger, then they retain their status of bread even if they no longer have the appearance of bread. Hence, one would recite "Ha'motzi" and Birkat Ha'mazon just as he would when eating ordinary, dry bread. If, however, the pieces in the soup are smaller than a Ke'zayit, then we no longer consider them "bread" with respect to Berachot, and one would recite "Mezonot" before eating the bread and "Al Ha'michya" afterward.
This ruling, however, applies only if one placed the soup in a "Keli Rishon," meaning, in the pot in which the soup was cooked over the fire. We speak here of a case where one removed the pot from the fire, and while the soup was still at or above the temperature of "Yad Soledet Bo" (where one's hand would instinctively recoil on contact) he placed bread in the soup. In such a case, one would recite "Mezonot" and "Al Ha'michya" if the pieces were of a volume less than thirty grams. If, however, one placed bread in his bowl of soup, he recites "Ha'motzi" and Birkat Ha'mazon regardless of the size of the bread, since the bowl is not the original utensil in which the soup was cooked.
The Mishna Berura (commentary to the Shulchan Aruch by Rabbi Yisrael Kagan, the "Chafetz Chayim," Lithuania, 1839-1933) adds (168:57) that in the case of small pieces of bread placed in soup, one does not recite Birkat Ha'mazon regardless of how much bread he eats. Generally, if a person eats 8 oz. of a food over which "Mezonot" is recited, he must recite Birkat Ha'mazon, as eating this amount constitutes the consumption of a meal. In our case, however, where one places small pieces of bread in a pot of soup, he recites "Al Ha'michya" rather than Birkat Ha'mazon even if he partakes of more than 8 oz. of bread.
Therefore, if one wishes to eat bread in his soup and prefers not to recite Birkat Ha'mazon, he should ensure that each piece amounts to less than thirty grams, and to place the pieces in the original pot in which the soup had been cooked on the fire.
Summary: One who places bread in his soup must recite "Ha'motzi" before eating the bread and Birkat Ha'mazon afterward, as one does over regular bread, unless the following two conditions are met:
1) Each piece of bread amounts to less than thirty grams;
2) The bread had been placed in the original pot in which the soup had been cooked.
If both these conditions are met, then one recites "Mezonot" before eating the bread and "Al Ha'michya" after eating the bread, regardless of the quantity of bread he eats.
