Put jícama crosswise into 1-inch-thick slices (make slices thinner if your cookie cutter is shallow). Lay 1 slice flat and cut out as many star-shaped chunks as possible. Cut chunks into 3/4-inch-thick stars using a mandoline or other manual slicer or a sharp thin knife.
< Sprinkle stars with lemon juice and arrange a parsley leaf on each. Drop 1/4 teaspoon tapenade onto center of each star, partially covering leaf.

Cooks' note:
• You can cut jícama stars 1 day ahead and chill, tossed with lemon juice, in a sealable plastic bag.