Gemara

40a (Rav Sheshes): Even if one said (between ha'Motzi and eating) "knead bran for the cattle," he need not bless again;

(Rav Yehudah): One may not eat before feeding his animals.

42a (R. Chiya bar Ashi): One must bless immediately after washing, without interruption.

52b (Beraisa - Beis Hillel): One must eat immediately after washing the hands.

This is another reason why it is better to wash after mixing the wine.

Rishonim

Rosh (Teshuvah 4:1): If one did his needs and wants to eat, after pouring once or twice on his hands and they are clean, he blesses Asher Yatzar and finishes the nnh and blesses Al Netilas Yadayim.

Hagahos Maimoniyos (Hilchos Berachos 6:17): Maharam (me'Rotenburg) was asked about one who eliminated and wants to eat [bread]. Must he wash again, or does one washing suffice for both? Ge'onim argue about this. It seems to me that one washing suffices for both, if he is sure that he washed in a way proper for a meal. Even though ha'Motzi must be Tekef to (right after) Netilah, Birkas Asher Yatzar is not a Hefsek, since it is also for Taharah of hands. It is no worse than "knead bran for the cattle," which is not a Hefsek. I found that Rashi holds like this, unlike R. Yakov ben Yakir, who said that he must wash again.

Mordechai (204): One may not have Hesech ha'Da'as (divert his mind) between Netilah and the meal, like it says in Berachos. If one came from the bathroom and washed his hands, some say that this does not help for a meal, for in between he blesses Asher Yatzar. This is a Hefsek not due to the meal, so he must wash again. This is not our custom. One need not wash again.

Hagahah: Maharam said that Asher Yatzar is not a Hefsek.

Hagahah: This is according to the opinion that Berachah may be Tekef to Mayim Rishonim. Rabbeinu Yehudah says that it refers to Mayim Acharonim. Some say that he dries his hands, blesses Asher Yatzar, and then Al Netilas Yadayim. Rashi says so. Orach Chayim] says that after pouring once and rubbing, he blesses Asher Yatzar, and later, while drying, he blesses Al Netilas Yadayim.

Tur (OC 165): Maharam used to do like R. Yakov ben Yakir. If he would wash once and bless Asher Yatzar and then Al Netilas Yadayim, this is a Hefsek. My father (the Rosh) used to do so. R. Peretz says that it is not a Hefsek. To be Machri'a (decide the issue), I say that after pouring once and rubbing, he blesses Asher Yatzar, and later, while drying, he blesses Al Netilas Yadayim.

Poskim

Shulchan Aruch (OC 165:1): If one did his needs and wants to eat, he washes twice. On the first washing he blesses Asher Yatzar, and on the second he blesses Al Netilas Yadayim.

Taz (1): Asher Yatzar is not a Hefsek, for Birkas Al Netilas Yadayim does not apply until drying.

Magen Avraham (1): If one eliminates in the middle of a meal, he need not bless ha'Motzi again. Therefore, he washes once, blesses Al Netilas Yadayim, and then Asher Yatzar. Even though he interrupts between Netilah and eating, some permit interrupting even between Netilah and ha'Motzi!

Magen Avraham (2): In 158:7 (regarding one who washed for wet fruit, and now wants to wash for bread), he washes again without a Berachah. There is different, for he initially washed without intent to eat (bread, so he cannot bless now for the first washing - Machatzis ha'Shekel). Here, he intended. Alternatively, here the first time he does not wash k'Halachah. (Eshel Avraham - he merely rinses his hands to clean them, without a Kli, or the water is not poured through a person.) The Beis Yosef connotes like this. This is primary. The Shlah says to touch a filthy place in between. I disagree. Since he washed properly, why should he cause Tum'ah and wash again and cause a Berachah?! Rather, he washes improperly the first time.

Kaf ha'Chayim (4): The Shlah's counsel is proper, for he causes himself to say a Berachah that he was obligated to say!

Gra (DH ha'Oseh): A proof that one washing suffices for both is from Rav and Reish Lakish, who say that one blesses on wine, Kidush, Ner and Havdalah (Pesachim 120b). One cup suffices for both (Kidush and Havdalah). The questioner in Teshuvas ha'Rosh connotes that one blesses Al Netilas Yadayim before Asher Yatzar. However, the Tur says that one blesses Asher Yatzar first. (The Rosh's son asked the question. Presumably, it was the Tur's brother - PF.) The Tur wrote that Maharam washed twice. Perhaps he holds like Rashi, just he was stringent l'Chatchilah like R. Yakov ben Yakir.

Mishnah Berurah (1): One should check if he needs to eliminate before washing.

Question (Taharas ha'Shulchan): Why can't he bless Asher Yatzar after ha'Motzi? One need not say Asher Yatzar immediately! See Be'er Heitev 7:1:

Note: Be'er Heitev brings from Maharshal that if one must bless Asher Yatzar and a Berachah Acharonah, he blesses Asher Yatzar first, for it is more frequent. He did not say that one must bless Asher Yatzar immediately!

Answer (Mishnah Berurah 2): It is improper to delay blessing Asher Yatzar until after ha'Motzi, for the obligation is immediately after eliminating. One should not delay it so much. The first time, one should not wash properly, only a little for the sake of cleanliness. Some Poskim say that Asher Yatzar is not a Hefsek between Al Netilas Yadayim and ha'Motzi. Therefore, if he washed properly for eating, he should bless Al Netilas Yadayim and then Asher Yatzar. One may do so l'Chatchilah if he has limited water and it is hard to wash twice.

Shulchan Aruch (ibid.): If he wants to wash only once, after pouring once on both hands and rubbing, he blesses Asher Yatzar, and while drying he blesses Al Netilas Yadayim.

Beis Yosef (DH Mi): The Tur says in the name of Maharam opposite to what it says in Hagahos Maimoniyos and Hagahos Mordechai, that one washing suffices for both. He says that Asher Yatzar is not a Hefsek between Al Netilas Yadayim and ha'Motzi. This shows that this opinion holds that he blesses Al Netilas Yadayim, and then Asher Yatzar. The Tur wrote oppositely, and also the Mordechai brings (that one blesses Asher Yatzar before Al Netilas Yadayim). If so, how did he write that it (Asher Yatzar) is a Hefsek? Al Netilas Yadayim is at the end, next to ha'Motzi! He must mean that Asher Yatzar is a Hefsek between washing and blessing Al Netilas Yadayim. Therefore, he was Machri'a that after pouring once and rubbing, which is before one may bless Al Netilas Yadayim, he blesses Asher Yatzar. Later, when it is time for Al Netilas Yadayim, i.e. while drying, he blesses it. Now, he blesses Al Netilas Yadayim in its time, and there is no Hefsek at all.

Beis Yosef (DH v'Chasav): Mahari Avuhav contested this. If after pouring once and rubbing he blesses Asher Yatzar, it was already proper to bless Al Netilas Yadayim, for the first pouring is Metaher the hands. If he wanted to dry his hands after the first pouring, they are Tehorim to eat! If so, Asher Yatzar is a Hefsek to Al Netilas Yadayim, for what he does afterwards (the second pouring) is to be Metaher the water on the hands, but not the hands themselves. Perhaps the Rav (the Tur) means that since the person should do a second pouring, even though it is only to be Metaher the first water, even so it is for the sake of Taharas Yadayim, for if he would touch where he dried his hands from the first water, his hands would become Tamei again. This shows that all this is needed to be Metaher his hands to eat. The Rosh wrote in Teshuvah 4:1 like the Tur said.

Taz (2): When one poured on both hands together, he may rub them together. If he poured on each hand by itself, he may not rub them (162:6). I say that it is better the first way, to wash twice. According to the second way, Mahari Avuhav's objection applies. He answered that the second pouring is needed for Taharah, lest he touch where he dried his hands. If so, if he poured a Revi'is on each hand or on both together, there is no need for a second pouring at all, so Asher Yatzar would be a Hefsek. People usually pour a Revi'is at once. This is proper, to avoid all concerns. Teshuvas ha'Rosh says to bless Asher Yatzar after his hands are clean, then finish washing and bless Al Netilas Yadayim. This connotes that he did not pour a Revi'is at once, for if so he need not finish washing. The Tur connotes unlike this. He said 'after he poured once.' This connotes that there is another pouring afterwards. If not, he should have said 'he should pour once on his hands...' Also, if he poured a Revi'is at once, he need not dry his hands (158:13)! However, the Maharshal disagrees. Since he did not pour a Revi'is at once, the question returns. Why did the Tur mention rubbing? It seems that one cannot bless Asher Yatzar and Al Netilas Yadayim adjacent to the other, for this is unlike R. Yakov ben Yakir, whom the Tur initially brought, since the Tur seeks to fulfill all opinions. Rather, a new action is needed before blessing Al Netilas Yadayim. This is why the Rosh said to pour once, i.e. if his hands are already clean from dirt, so only two pourings are needed. He pours once, blesses Asher Yatzar, then does a new action, i.e. the second pouring, and blesses Al Netilas Yadayim. If his hands were initially dirty, he must pour three times, so first he pours twice, (blesses Asher Yatzar, pours a third time, and blesses Al Netilas Yadayim). The Tur discusses when his hands were clean. He says that he rubs after pouring to teach that he was Yotzei Netilah, since he may rub his hands. If so, the second pouring is a new act for the need of Netilas Yadayim. This is when he does not pour a Revi'is at once. Sometimes one pours a Revi'is at once, and it is a Hefsek. Therefore, the first way is better.

Magen Avraham (3): He rubs the hand on itself, i.e. the fingers on each other. Alternatively, he pour a Revi'is at once on each hand. (Then he may rub them together.) The Bach says that even so, the time for the Berachah is only when he dries. I say that he washed both hands together (with less than a Revi'is - Machatzis ha'Shekel). This answers Mahari Avuhav's question. If he forgot to bless until he washed (Levushei Serad - this should say "dried") his hands, he blesses Al Netilas Yadayim, and then Asher Yatzar, like Hagahos Maimoniyos.

Gra (DH u'Meshafshef): This is like the Rosh, who say that one must rub the hands. R. Shimshon holds that Shifshuf is drying the hands. Therefore, the Poskim omitted this (rubbing).

Eliyahu Rabah (2): It is best not to intend the first time for eating.

Kaf ha'Chayim (1): Rashi holds that Asher Yatzar is not a Hefsek. One may bless either first. The Bach says to bless Asher Yatzar first, for its Chiyuv came first. I say that one should first wash three times alternating, due to the Ru'ach Ra'ah of a bathroom, dry his hands, bless Al Netilas Yadayim, and then wash for bread. If he lacks the water or time for this, he washes three times alternating, rubs his hands, blesses Asher Yatzar, lifts the, and blesses Al Netilas Yadayim before drying them.

Kaf ha'Chayim (2): If he forgot Asher Yatzar until blessing Al Netilas Yadayim, he says Asher Yatzar after ha'Motzi. He should not put any accompaniment on his bread before Asher Yatzar, lest he forgot to bless it.

Mishnah Berurah (3): Acharonim say that since we pour a Revi'is at once, it is better to do the Shulchan Aruch's first counsel. See what I wrote above (2).

Kaf ha'Chayim (3): If he will eat wet fruit after eliminating, all agree that he washes only once.

Kaf ha'Chayim (4): It is best to wash the first time improperly, e.g. with a broken Kli or water Pasul for Netilas Yadayim. If he cannot, and he cannot wait until his mind was diverted from eating, he washes the first time with intent only for Ru'ach Ra'ah.

Aruch ha'Shulchan (2): Not everyone is proficient about the proper way to wash twice. It is best to wash once, and to say Asher Yatzar after Al Netilas Yadayim. It is not a Hefsek, like Rashi says.

Teshuvos v'Hanhagos (1:168): I heard that it is best to wash once, and to bless Al Netilas Yadayim before drying, and Asher Yatzar after drying. It is merely 'good to be careful' not to talk between drying and ha'Motzi. Regarding Asher Yatzar, one need not be careful. The Chafetz Chaim himself did so, and the Chazon Ish (24:30 DH keshe'Tzarich) says that this is the custom.

Dinim v'Hanhagos (6:8): The Chazon Ish himself conducted like this, and so did the Steipler (Orchos Rabbeinu 1 p.78).

Halichos Shlomo (20:26): It is best to wash first from the faucet, say Asher Yatzar, and then wash from a Kli.

Ketzos ha'Shulchan (33:14): One can wash using a Kli, and after washing each hand he touches it to the other hand, for this is invalid for a meal.