Q. During the Seder shel Pesach, may I interrupt the saying of Hallel to speak about a section to which I wish to draw the family’s attention so that they may think about this idea or concept when they are reciting the specific passage of Hallel, or does this explanation constitute a Hefsek and make reciting the blessing at its conclusion a problem?

A. Rishonim disagree whether Hallel is recited with a brocho before starting, during the seder. (See Tur end of 473 and Mishna Berura 480: 1). Although our tradition is not to say a brocho before, Horav Shlomo Miller’s Shlit’a opinion is that one should not be mafsik lechatchila while reading it. The reason, he pointed out, is quoted in Biur Halocho in the name of Ramban (473: 2; D;H; hareshus beyodo), namely that once the cup of wine has been filled, one should not be mafsik. The Rov added since “ein masichin al kos shel brocho” (Brochos 51b).
As important as explaining what is being said is on the night of Pesach is, one should explain before or after the reading.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a