1. Heat oven to 350 degrees F. In medium bowl, combine flour, baking powder, and salt. Set aside. In large bowl, with mixer on high, beat shortening, butter, and granulated sugar until light and fluffy, about 3 minutes. Beat in egg, egg yolk, and vanilla until well blended. With wooden spoon, stir in flour mixture until well combined.
2. In small bowl, combine brown sugar and cinnamon. Shape heaping tablespoons of dough into balls, drop into cinnamon-sugar mixture, and roll to coat. Place 2 inches apart on baking sheets, and bake until golden, about 15 minutes. Cool completely.
3. Place melted chocolate in resealable plastic bag. Snip off one corner, and pipe snowflake design onto each cookie. Let set 15 minutes.