What *is* charoset?

They brought before him matzah and ḥazeret and ḥaroset, and at least two cooked dishes, although eating ḥaroset is not a commandment.

Rabbi Eliezer ben Tzadok says: it is a commandment.

And if it is not a mitzvah, why does one bring it? Rabbi Ami said: It is brought due to the poison (kappa) in the bitter herbs, which is neutralized by the ḥaroset...

Rabbi Elazar, son of Rabbi Tzadok, says that eating ḥaroset is a mitzvah. What is the nature of this mitzva?

Rabbi Levi says: It is in remembrance of the apple.

And Rabbi Yoḥanan says: It is in remembrance of the clay.

Abaye said: Therefore, to fulfill both opinions, one must prepare it tart and one must prepare it thick: tart in remembrance of the apple, and one must prepare it thick in remembrance of the clay.

It was taught in a baraita in accordance with the opinion of Rabbi Yoḥanan: The spices (tavlin) used in the ḥaroset are in remembrance of the straw (teven), and the ḥaroset is in remembrance of the clay.

Rabbi Elazar, son of Rabbi Tzadok, said: The small shopkeepers in Jerusalem would say as follows: Come and take spices for the mitzvah.

Rabbi Joshua ben Levi said, it has to be thick. That is to say, in remembrance of the clay.

There are Tannaim who state, it has to be soft [or runny]. That is to say, in remembrance of the blood.

...and when the Israelite women conceived, they would return to their homes. When they were about to go into labor, the women would go out into the fields and give birth in the apple orchards, as it is written: "I roused you under the apple tree" (Song of Songs 8:5).

And the Holy Blessed One would send an angel from the heavens who cleaned them and made them beautiful... and would grant them two round cakes, one of oil and the other of honey...

In remembrance of the apple-- In Tractate Sotah, it says that they would give birth to their children under the apple trees without pain, so that the Egyptians wouldn't know, as it is written: "I roused you under the apple tree."

One must prepare it tart and one must prepare it thick-- in the Yerushalmi it says that it should be made in remembrance of the blood, and therefore we refer to it as dipping, like into a liquid. This is what the people follow: at the time of eating, they thin it out with wine or vinegar.

And in the responsa of the Geonim, it is explained that charoset is made from fruits that are compared to the Jewish people in the Song of Songs [apples, pomegranate, fig, date, walnut, almond].