Making a meal on Mezonot
Someone who eats a snack of Pas HaBah Bekisnin makes Mezonot and Al HaMichya and one who eats a meal of Pas HaBah BeKisnin makes HaMotzei and Birkat HaMazon.  The details of what's considered a meal will be explained B"H in this article.
What is considered a meal for Pas Habah Bekisnin?
- All food that’s eaten during a meal is included as long as one Kezayit of Pas HaBah Bekisnin is eaten within Kedi Achilat Pras (4 minutes). 
- According to Ashkenazim if one makes a meal out of Pas HaBah BeKisnin one should wash with a bracha (of Al Netilat Yadayim) and make HaMotzei. However, Sephardim hold that one should wash without a bracha but one would have what to rely on to wash with a bracha. 
Amount of a meal when Pas Haba Bekisnin is eaten alone
- According to Ashkenazim, if one eats less than 8 kezaytim one should certainly make a Mezonot. If one eats the amount of a regular meal one should make HaMotzei. [For a regular person if one eats 280 grams of regular cake one certainly is having the amount of a regular meal and could make HaMotzei and Birkat HaMazon.] Preferably, one shouldn't have in between 8 Kezayitim and the amount of a regular meal. After the fact (if one ate between 8 Kezayitim and a definite meal), if one is not full make Al HaMichya and if one is full make Birkat HaMazon, yet, in such a case it’s preferable to hear Birkat HaMazon (from someone who’s obligated to make Birkat HaMazon) or to eat bread (making HaMotzei and Birkat HaMazon). [For background see footnote.]
- According to Sephardim, if one ate less than 6 Kezaytim one should make a Mezonot. If one eats more than 8 Kezayitim one should make HaMotzei. Preferably one shoudln't eat between 6 and 8 Kezaytim and if one did then one should just make Al HaMichya. [For background see footnote.]
Amount of a meal when eaten together with other foods
- According to Sephardim even if Pas Haba BeKisnin is eaten with other foods those other foods are not taken into consideration when considering the amount of a meal.  However, according to Ashkenazim the following laws apply:
- One shouldn’t eat a Kezayit of Pas HaBah Bekisnin together with other foods (any food even if it’s not Melaftim Et HaPat) if altogether there’s a shuir of 8 Kezayitim whether one has in mind to establish a meal or not. 
- A practical advice is to eat the Pas HaBah Bekisnin, make Al Hamichya, and then eat the other foods, or eat the other foods, make Bracha Achrona, and then eat the Pas HaBah Bekisnin. However, this advice isn’t applicable if the other foods include mezonot (such as rice or noodles) because of making an unnecessary Bracha. 
- After the fact, if one ate less than 8 Kezayitim of Pas HaBah Bekisnin even if one’s full, one should make an Al Hamichya, Similarly, if one ate more than 8 kezaytim of Pas HaBah Bekisnin together with foods that don’t accompany bread (such as farfel, rice, fruit, or sweets) and if full from everything together, one should make a Al HaMichya unless one was full from the Pas HaBah Bekisnin alone in which case one should make Birkat HaMazon. If one ate more than 8 kezaytim of Pas HaBah Bekisnin together with foods that accompany bread (such as meat, fish, cheese, or vegetables) and if full from everything together, one should make Birkat HaMazon. 
- The only way to make a HaMotzei without a doubt is to:1)eat bread, 2)have 20 kezaytim of Pas HaBah Bekisnin alone, or 3)have 8 kezaytim of Pas HaBah Bekisnin together with foods that accompany bread (such as meat, fish, cheese, vegetables). 
Changing one's mind
- If one started the meal thinking that one was going to have 8 Kezayitim and then changed his mind and couldn’t finish all 8 Kezayitim, one may finish eating based on his orginal HaMotzei and concludes with a Al HaMichya. 
- If one made a Mezonot thinking that one was only going to have a few Kezayitim and then changed his mind to end up having 8 Kezayitim, if one plans on having another 8 Kezayitim one should stop and wash with a bracha and make HaMotzei.
- If one made Mezonot planning to have a few Kezyitim, and then changes to have another few Kezayitim and in total all he ate will add up to 8 Kezayitim one shouldn’t make any new bracha upon changing one’s mind, however, if one started thinking that one would not have more than a certain amount and now clearly changes his mind about that, one should make a new Mezonot. Nonetheless, one concludes with Birkat HaMazon. 
Keviut Seduah on Shabbat
- There’s no difference between Shabbat and the rest of the week regarding the status of the Pat habah BeKisnin. 
- If a Sephardi is eating at an Ashkenazic family who is having sweet challah for Hamotzei, ideally, one should eat 8 or at least 6 kezaytim of mezonot in order to be able to make HaMotzei and Birkat HaMazon, however, since that's usually very difficult there is what to rely on to make a HaMotzei and Birkat HaMazon even if one only eats a Kezayit of the sweet Challah. 
- S”A 168:6
- The Kaf HaChaim and Sh”t Korban Eshe write that one needs to have all of the 4 Kebayitzim in one Kedi Achilat Pras. However, Yalkut Yosef (Birkat HaMazon pg 130) writes that the strict halacha only requires that one have one Kezayit in a Kedi Achilat Pras. Vezot HaBracha (Chapter 4, pg 27) agrees with Yalkut Yosef.
- Mishna Brurah 158:8, Yalkut Yosef (Kitzur S”A 168:8)
- See next note
What’s the Bracha on Pas HaBah Bekisnin?
- The opinion of Rav Nachman and Shmuel in Gemara Brachot 42b is the Bracha on Pas HaBah Bekisnin is Mezonot when eaten as a snack and HaMotzei when eaten as a meal. Rashi (Brachot 41b s.v. Pas) and the Rif 30a holds that if one eats Pas HaBah Bekisnin as a snack there’s either no Bracha Achrona at all or there’s only a Boreh Nefashot (see Rabbenu Yonah’s (29b s.v. Trisar) two explanations of the Rif and Tosfot’s (D”H Elah) explanation of Rashi). However, Tosfot (41b s.v. Elah) explains that the Bracha Achrona on Pas HaBah Bekisnin is Al HaMichya (if one doesn’t make it into a meal). The Rosh 6:30, Rashba s.v. Rav Huna, and Rambam (Brachot 3:9) agree with Tosfot and the Tur and S”A 168:6 codify this as halacha that for a snack one makes Mezonot and Al HaMichya and a meal one makes HaMotzei and Birkat HaMazon.
- The Bet Yosef 168:6 quoting the Shibolei HaLeket (Siman 159), Magen Avraham 168:13, and Chaye Adam 54:14 in name of the Gra hold that the amount of meal for this halacha is the amount people normally eat at a regular meal in the morning and evening. (Mishna Brurah 168:24 and Shaar HaTziyun 19 also quote the Sefer Eshkol and Shagat Aryeh). However, the Birkei Yosef 186:4 and Kaf HaChaim 168:45 argue that the amount of a meal in this context is the same as a meal for Eruv Chatzerot which is either 3 or 4 KeBaytzim.
- Ashkenazim: The Mishna Brurah 168:24 rules that the halacha follows the opinion that a meal is considered by a regular meal people eat but adds that it's proper to be strict for those who are strict to require 4 KeBaytzim (meaning, that preferably one should only eat less than 8 Kezayitim or more than the amount of a regular meal, Vezot HaBracha pg 29). VeZot HaBracha (chap 4, pg 31) writes that according to his calculation for a regular person for regular cake if one eats less than 230 grams that is considered a snack, if one eat more than 280 grams that is certainly a meal. He continues that if one did eat in between 8 Kezayitim and a certain meal, if one is not full make Al HaMichya and if one is full make Birkat HaMazon, yet, in such a case it’s preferable to hear Birkat HaMazon (from someone who’s obligated to make Birkat HaMazon) or to eat bread (making HaMotzei and Birkat HaMazon).
- Sephardim: Halacha Brurah 168:16 (explained in Otzorot Yosef Siman 9) writes that Sephardim hold like the Chida that if one ate 8 Kezayitim one should make HaMotzei and Birkat HaMazon, and if one ate less than that one should make Mezonot and Al HaMichya but it's preferable that one shouldn't eat in between 6 and 8 Kezayitim.
- Kaf HaChaim 168:47 rules against the Magen Avraham 168:13 and says that S”A implies that one must be the amount of a meal from the Pat itself.
- Mishna Brurah 168:24, Vezot HaBracha (Chapter 4, pg 32-3). Vezot HaBracha (pg 33) adds that there’s what to rely on to eat less than 8 Kezayitim of Pas HaBah Bekisnin together with food that’s not Melafet HaPat (rice, couscous, noodles, fruit, or sweets but not meat, fish, cheese, or vegetables) and make a Mezonot and Al HaMichya.
- Vezot HaBracha (Chapter 4, pg 33). Vezot HaBracha (Birur 7 pg 234) adds that if the other foods are Tavshil Mezonot (like rice and noodles) and the above advice isn’t applicable, there’s what to rely on to eat Pas HaBah Bekisnin at the end of the meal after one ate the other foods (without making a Bracha achrona on the other foods).
- Vezot HaBracha (Chapter 4, pg 33 note 11)
- Vezot HaBracha (Chapter 4, pg 31 and pg 33 note 11)
- Sh”t Igrot Moshe O”C 2:54, Yalkut Yosef (Birkat HaMazon pg 137).
- Mishan Brurah 168:25 writes that if one changed one’s mind one doesn’t make a new HaMotzei if one doesn’t plan on eating more than 8 Kezayitim. Mishna Brurah (Shaar Tzion 168:21) writes that one shouldn’t make a new Mezonot unless one clearly changed one’s mind such as if when he started he thought that he will not eat more than a certain amount, however, if one didn’t clearly retract his opinion then one doesn’t make a new Mezonot.
- Kaf HaChaim 168:48.
- Vezot HaBracha (Chapter 4, pg 39) in name of Rav Mordechai Eliyahu and Rav Elyashiv paskening for Sephardim