See this post by Menachem Butler for references to literature on machine-made matzah. My custom is to use machine-made shemurah matzah for the mitzvah of eating matzah at the seder whenever it is available.

שלחן ערוך או”ח תנט:ב

לא יניחו העיסה בלא עסק ואפילו רגע אחד. וכל זמן שמתעסקים בו, אפילו כל היום אינו מחמיץ; ואם הניחו בלא עסק שיעור מיל, הוי חמץ. ושיעור מיל הוי רביעית שעה וחלק מעשרים מן השעה. הגה: ויש להחמיר למהר בענין עשיית המצות, כי יש לחוש שהשהיות יצטרפו לשיעור מיל, או שיהיה במקום חם שממהר להחמיץ…

באר היטב ס”ק ח

In a blog post (here) that brings a wide variety of artistic representations of the Last Supper, David Assaf wrote that some people either don’t know, or forget, that the Last Supper was a Passover Seder.

לפעמים אנו שוכחים – או שמא פשוט לא יודעים – שהסעודה האחרונה של ישו היתה סעודת ליל הסדר.

The claim that the Last Supper was a Passover Seder is repeated by many and rarely doubted, but the problem is that this claim is probably incorrect.

Assaf brings the following text from Matthew 14:12-26:

12 And on the first day of Unleavened Bread, when they sacrificed the Passover lamb, his disciples said to him, “Where will you have us go and prepare for you to eat the Passover?” 13 And he sent two of his disciples and said to them, “Go into the city, and a man carrying a jar of water will meet you. Follow him, 14 and wherever he enters, say to the master of the house, ‘The Teacher says, Where is my guest room, where I may eat the Passover with my disciples?’ 15 And he will show you a large upper room furnished and ready; there prepare for us.” 16 And the disciples set out and went to the city and found it just as he had told them, and they prepared the Passover. 17 And when it was evening, he came with the twelve. 18 And as they were reclining at table and eating, Jesus said, “Truly, I say to you, one of you will betray me, one who is eating with me.” 19 They began to be sorrowful and to say to him one after another, “Is it I?” 20 He said to them, “It is one of the twelve, one who is dipping bread into the dish with me. 21 For the Son of Man goes as it is written of him, but woe to that man by whom the Son of Man is betrayed! It would have been better for that man if he had not been born.” 22 And as they were eating, he took bread, and after blessing it broke it and gave it to them, and said, “Take; this is my body.” 23 And he took a cup, and when he had given thanks he gave it to them, and they all drank of it. 24 And he said to them, “This is my blood of the covenant, which is poured out for many. 25 Truly, I say to you, I will not drink again of the fruit of the vine until that day when I drink it new in the kingdom of God.”

In one of the most important articles on the possible relationship between the Last Supper and the Passover Seder, Jonathan Klawans wrote:

While three of the four canonical Gospels strongly suggest that the Last Supper did occur on Passover, we should not get too comfortable based on that. The three Gospels that support this view are the three synoptic Gospels—Matthew, Mark and Luke. As anyone who has studied these three Gospels knows, they are closely related. In fact, the name synoptic refers to the fact that these three texts can be studied most effectively when “seen together” (as implied in the Greek etymology of synoptic). Thus, in fact we don’t really have three independent sources here at all. What we have, rather, is one testimony (probably Mark), which was then copied twice (by Matthew and Luke).

Klawans continued and wrote:

Against the “single” testimony of the synoptics that the Last Supper was a Passover meal stands the lone Gospel of John, which dates the crucifixion to the “day of Preparation for the Passover” (John 19:14). According to John, Jesus died just when the Passover sacrifice was being offered and before the festival began at sundown (see the sidebar to this article). Any last meal—which John does not record—would have taken place the night before, or even earlier than that. But it certainly could not have been a Passover meal, for Jesus died before the holiday had formally begun.

Klawans admitted that the description found in John is not without problems, but for a number of reasons he finds it to be more reliable than the synoptic version. You can read here and here for reactions to Klawans’s article.

And what about the seder itself? Again, from Klawans:

How much of the Haggadah goes back to ancient times? In the 1930s and 1940s, the American Talmud scholar Louis Finkelstein (1895–1991) famously claimed that various parts of the Passover Haggadah were very early, stemming in part from the third century B.C.E. In 1960, Israeli scholar Daniel Goldschmidt (1895–1972) effectively rebutted practically all of Finkelstein’s claims. It is unfortunate that Goldschmidt’s Hebrew article has not been translated, because it remains, to my mind, the classic work on the early history of the Passover Haggadah. Fortunately, a number of brief and up-to-date treatments of the history of the Haggadah are now available. A full generation later, the Goldschmidt-Finkelstein debate seems to have been settled, and in Goldschmidt’s favor. Almost everyone doing serious work on the early history of Passover traditions, including Joseph Tabory, Israel Yuval, Lawrence Hoffman, and the father-son team of Shmuel and Ze’ev Safrai, has rejected Finkelstein’s claims for the great antiquity of the bulk of the Passover Haggadah. What is particularly significant about this consensus is that these scholars are not radical skeptics. These scholars believe that, generally speaking, we can extract historically reliable information from rabbinic sources. But as demonstrated by the late Baruch Bokser in his book The Origins of the Seder, practically everything preserved in the early rabbinic traditions concerning the Passover Seder brings us back to the time immediately following the Roman destruction of the Temple in 70 C.E. It’s not that rabbinic literature cannot be trusted to tell us about history in the first century of the Common Era. It’s that rabbinic literature—in the case of the Seder—does not even claim to be telling us how the Seder was performed before the destruction of the Temple.

Or as my friend Josh Kulp put it,

This overwhelming trend among historians and rabbinic text critics leads to the conclusion that Jesus’ last supper, even if it did occur on the eve of Passover, was not a ‘seder’, for there was no ‘seder’ in the Second Temple period.

Update: See some of my comments (Hebrew) to the original post by David Assaf.

Update II: See the following quotation from the Anchor Bible Dictionary’s entry on “Last Supper” for an example of how some scholarship presented the material in the Mishnah as an accurate portrayal of practice during the Second Temple period.

Although a number of scholars identify the Last Supper as a Passover meal, a description of which is given in the Mishnah (Pesaḥ10; cf. Str-B 4/1: 41-76), the majority are still not convinced of this interpretation. However, many would concede that Jesus ate his final meal in a Passover atmosphere; there was, after all, the proximity of the feast.

Hag Kasher ve-Sameah.

Trans.: This is the bread of poverty which our ancestors ate in the land of Egypt. Let all who are hungry come and eat. Let all who are needy come and celebrate the Passover. At present we are here; next year may we be in the land of Israel. At present we are slaves; next year may we be free. (The Shechter Haggadah, 28)

The Ha Lachma Anya section of the Passover Haggadah is unique because most of it is in Aramaic, while the rest of the Haggadah is in Hebrew. For hundreds of years scholars have been trying to explain why this portion is in Aramaic. Here is the summary by Josh Kulp in the Schechter Haggadah. (191)

This opening declaration appears in geonic Haggadot and in most manuscripts and geniza fragments of the Haggadah, but does not appear in ancient Eretz Yisraeli Haggadot. Although a few elements of the paragraph are found in the Bavli, they are not presented there in the context of the Pesah seder. According to Safrai (111) the statement is a geonic composition and thus in Aramaic. Early prayers were composed in Hebrew, but in the geonic period prayers, announcements, monographs and responsa were frequently written in Aramaic. Indeed, even the Hebrew words (לשנה הבאה, בני חורין) appear in earlier versions of the Haggadah in Aramaic. The Hebrew words are Hebraisms of later copyists.

This section was intentionally written in Aramaic so that as many people as possible could understand it, but what happens when people aren’t able to understand either this section or other parts of the Haggadah? There is evidence that already in the Geonic period different parts of the Haggadah were being translated. Rav Natroni Gaon is said to have translated the Mah Nishtanah for the members of his household. (Shaarei Simcha, vol. 2, 102)

The entry Haggadah from the Jewish Encyclopedia has the following.

From early days it has been customary to translate the Haggadah into the vernacular for the benefit of children. Aaron ha-Kohen of Lunel (14th cent.) mentions it as a laudable custom, and says that it was done in England (Moses Isserles, in his commentary on Ṭur Oraḥ Ḥayyim, 473).

This statement is based up a comment by R. Moses Isserles found in his Darchei Moshe, OH par. 473.

Trans. Rabbi Yisrael Bruna wrote, “One should say Ha Lachma in a language that the children and women understand. This is what R”i from London (?) did, he translated the entire Haggadah into the vernacular in order that the children and women would understand.” The Kol Bo wrote that this is a proper custom.

The entry from the JE is a bit misleading, since the Kol Bo, i.e. R. Aharon ha-Cohen of Narbonne, didn’t comment on the custom to translate the entire Haggadah, he spoke about the custom to translate the Ha Lachma and Ma Nishtanah sections, emphasizing how important it is that people understand not only the questions, but the also the answers.

There are a number of other instances of medieval sources testifying to translations of parts of the Passover Seder. See some of these sources that are brought by R. Kasher in Haggadah Shleimah, 109.

An interesting case of a Haggadah translation was done by an Italian woman. Yael Levin has written here (English) and here (Hebrew) about Flora Randegger-Friedenberg, a nineteenth century Italian Jewish woman who translated the Haggadah into Italian.

For over a thousand years, people have been trying to enable others to both understand and find the Haggadah meaningful, may we succeed in doing so this year.

I wasn’t sure if this was anti-humra medicine, or anti-hametz (hamira) medicine. Although it is a long way until Purim, I wonder what some side effects might be.

Rabbi Yigal Sklarin, Talmud & Jewish History Teacher, Ramaz:
Using Italian Renaissance Art to Understand Halacha: The Laws of Mezuzah in Renaissance Italy

The common denominator of all the Halakhic codifiers who mention this minhagh is easy to spot: they all resided in France.
…
What of Germany (Ashkenaz)? The medieval authorities there were either silent or openly opposed to the custom, exemplified by this statement of R. Ya’aqov, son of the Rosh, in his famous work the Tur: “This is an extreme stringency and it is not the custom”.

This is incorrect for two reasons. The first is that the custom was also known in Provence which is NOT the same geographic, cultural, nor halakhic area as Northern France. They must be treated as two distinct areas. The second reason is that we know that the prohibition of not eating kitniyot was already an established custom in Germany in the early 13th century. Dr. Simha Emmanuel has published from a ms. the sermon on Passover of Rabbi Eliezer of Worms (1176-1238). In his sermon Rabbi Eliezer states that “ומה שאין אוכלין פולין ועדשים, מפני שיש בהן חיטין” (“And that which they don’t eat beans and lentils is because they have in them wheat.”) See here. Not only does he state as a given the existence of this custom, but he also gives a different reason and this being that mixed in with “beans and lentils” is wheat. This reason for the prohibition reflects the reality of the most important new agricultural practice of this time period, the three-field rotation system. See the following quote from here.

Still another component of the Agricultural Revolution of the Middle Ages was the development of the three-field rotation system. The classic two-field farming system of the Mediterranean regions of antiquity typically involved farming one field while leaving another fallow. In the new three-field pattern that arose on the European plain, arable land was divided into three fields with plantings rotated over a three-year cycle: two seasonal plantings employed two fields, a winter wheat crop and a spring crop of oats, peas, beans, barley, and lentils, with the third field left fallow.

As I said before, do whatever you want regarding the customary prohibition of eating kitniyot during Passover, but the claim that it has no basis in reality is now known to most likely be untrue.