As far as I know mitzvot such as eating marror or saying hallel at the Pesach seder are only rabbinic (the marror was biblical previously but I am told that is no longer so). If this is the case and ...
Whenever a Jew performs an activity that is mandated by the Torah, s/he recites the blessing that acknowledges God, "אשר קדשנו במצוותיו" (who sanctified us with his commandments), and who commanded us ...
Should one refrain from making a Berachah on rabbinically prohibited foods, or does that rule only apply to biblically prohibited foods?
During the Pesach seder, but not during the rest of Pesach, we say b'rachot for the mitzvot of matzah and maror. (I mean the "asher kidshanu b'mitzvotav" b'rachot.) So it seems that we are only ...