Heat oven to 375. In large bowl, combine sugar and butter until light and fluffy. Add vanilla and egg; blend well.
Stir in flour, baking powder, salt and orange zest. Roll dough into 1" balls and place 2" apart on ungreased cookie sheet. Flatten with the bottom of a glass dipped in sugar.
Bake at 375 for 6-8 minutes or until edges are lightly browned. Cool for 1 minute and transfer to cooling rack to let cool completely.
Combine glaze ingredients and melt in microwave. To do this, heat for 1 minute; stir. Heat for 30 seconds; stir. Repeat heating for 30 second intervals until most chips are melted, stirring in between each cycle.
Dip 1/2 of each cookie into the glaze. Shake off excess and place dipped cookies on a cookie sheet that has been lined with wax paper. Chill in fridge until glaze is set, about 10 minutes.