Is there such a halacha that someone can have kavana by the bracha of ha-motzei to patur all the of the mezonos (including cake, cookies, etc) that they might eat in the middle (or end) of the seudah?
What about when someone is eating a Shabbos seudah where only the baal habayis is going to make ha’motzei and be motzee everyone else. How can one have “kavana” then in order to avoid any problems of eating mezonos in the middle of the seudah.
This idea of having explicit intention for mezonos during the meal is mentioned by a number of authorities, but it is not the ideal method.
A person can have the intention even if the ba’al habayis reciting the berachah doesn’t.
It is true that this advice is given by a number of poskim, as mentioned by the Biur Halachah (168) in the name of the Chayei Adam (58:2). The Olas Tamid also writes that when one has explicit intention to include the mezonos, this helps, and this is also mentioned by the Mishnah Berurah in the name of Halachah Berurah (disciple of the Magen Avraham).
Yet, it is hard to understand how this can help.
Rabbi Yechiel Michel Stern (Birkas Hanehenin p. 58) asks the question of how such intention will help: If the pas haba be-kisnin is not considered bread, it follows that the berachah of Hamotzi will not help.
Indeed, from the wording of the Magen Avraham (168:35) it appears that Hamotzi never helps for pas haba be-kisnin, and even a person’s explicit intention will not help for this purpose.
However, many authorities rule that bedieved, the berachah of Hamotzi helps for pas haba be-kisnin (Even Ha-Ozer 168:5; Kitzur Shulchan Aruch 56:1; Kerem Shlomo 168:5; Kaf Hachaim 168:43). This is also stated by the Ritva (Hilchos Berachos 2:18).
[However, see Maamar Mordechai 168:18.]
Based on the ruling that bedieved the berachah of Hamotzi helps, it can be explained that in cases of safek pas (a food that might be considered bread, but might not), it is permitted to rely lechatchilah on one’s explicit intention that the berachah should include the food.
The rationale for this remains somewhat unclear, and the best option is to make a berachah on a little mezonos before the meal, and the next best is to have explicit intent, which though slightly difficult to understand, is endorsed by the poskim.