Shulchan Menachem. We are learning Chapter Reish Lamed Tes, 239, discussing the customs of charoses at the Seder according to Chabad practice.
We know that one of the distinguishing features of the Seder is dipping twice: first the karpas in salt water, and then the maror in charoses. The charoses is prepared from apples, pears, and nuts, following the minhag, without adding other ingredients that were historically avoided due to chametz concerns.
Although charoses is prepared before Yom Tov, the wine is not mixed in at that time. Rather, just before dipping, the charoses is softened with wine. The Rebbe notes that the wine used is from the Seder itself—specifically from the overflow of the kos, as the cup is filled to the point that it spills over.
There are two times we dip maror in charoses: once when eating maror alone, and again during Korech. However, a complication arises for those who are careful about Gebrokts, avoiding any liquid coming into contact with matzah.
When making Korech, the maror is placed together with the matzah. If one were to dip the maror at that point, the charoses could come into contact with the matzah, raising concerns of Gebrokts. Therefore, the minhag of the Rebbeim was not to dip in the usual manner in this case.
Instead, one takes dry charoses and places it onto the maror, and then shakes it off. This ensures that the maror has contact with charoses, fulfilling the intent of the mitzvah—removing the sharpness of the maror—while avoiding any moisture touching the matzah.
This stringency applies specifically when matzah is involved, such as by Korech. When eating maror alone, there is no concern, and the usual dipping can be done.
Summary
Charoses is softened with wine only at the time of use, and maror is dipped twice. For those careful with Gebrokts, dry charoses is applied and removed to avoid contact with matzah, preserving both the minhag and the stringency.