Place crackers in a large plastic bag and crush them to fine crumbs, using a rolling pin or mallet. Add parsley, herb seasoning, salt and cayenne and shake to combine.
In a separate plastic bag, combine the scallops and mustard. seal the bag, and squish around to coat the scallops with the mustard. Add the scallops to the cracker mixture, seal the bag, and shake to coat evenly.
Heat the oil in a large skillet over medium heat. Remove the scallops from the bag, place in the skillet, and cook until golden brown on the outside and opaque on the inside, about 3 minutes per side.