Beat first six ingredients at medium speed with an electric mixer until dry ingredients are moistened. Press dough evenly into 2 lightly greased 9-inch tart pans or cakepans.
Bake at 350° for 25 minutes or until lightly browned. Let stand 5 minutes. Cut each shortbread into 12 wedges. Place wedges on a large ungreased baking sheet; bake 5 more minutes or until crisp. Remove to wire racks to cool. Trim coconut from edges of shortbread; drizzle with melted chocolate, if desired.
To make ahead: Place baked and cooled shortbread wedges between layers of wax paper in an airtight container, and freeze up to one month, if desired. Bring to room temperature and drizzle with melted chocolate before serving.