In a medium bowl, mix together the chickpeas, cucumber, scallions, garlic, lemon juice and zest, cumin, paprika, and salt. You can make the salad up to this point and keep it in the fridge for up to 2 days.
Stack the mustard green leaves with the largest at the bottom, smallest at the top. Trim away the stem and discard. Roll the leaves width-wise into a cigar. Turn the roll over so that the opening is touching the cutting board. Thinly slice the cigar - the result will be beautiful ribbons of mustard greens.
When you are about ready to eat, fold in the mustard greens and parsley with the chickpea mixture. Taste for seasoning and add more salt and lemon juice as needed. Serve at room temperature.