Finely grate orange peel to measure 2 tablespoons of orange peel. Set aside.
In a large bowl, Beat butter and sugar, with an electric mixer on medium speed, until light and fluffy. Beat in egg, orange extract and grated orange peel until well blended, scraping down sides of bowl. Gradually add flour. Beat at low speed until well blended, scraping down side of bowl occasionally. Stir in additional flour with spoon to form a soft dough. Form dough into a ball, wrap in cellophane and chill in refrigerator until firm or at least 1 hour.
Preheat oven to 400ºF. Grease cookie sheets.
Place dough on a lightly floured surface and roll out to 4” thickness. Cut dough into 2x1” bars. Place bars 2” apart on prepared cookie sheets.
Bake 10 minutes or until lightly browned. Remove cookies with spatula to wire rack to cook completely.
Melt chocolate in a 1 cup glass measuring cup or microwave safe container, at medium power for 3-4 minutes, stirring until smooth.
Dip on end of cookie ½ way up, allowing excess to drip back into cup. Transfer cookie to waxed paper for 1 hour or until set.