Step #2 Brush 2 baking sheets very lightly with oil.
Step #3 Sift the flour, baking soda, baking powder & salt into a medium bowl.
Step #4 Whisk the buttermilk & vanilla together in a liquid measuring c.
Step #5 Set aside.
Step #6 Beat the butter In a large-ish bowl with an electric mixer until smooth.
Step #7 Gradually add the sugar & continue to beat at high speed until light & fluffy, about 5 mins.
Step #8 Add the eggs & yolks, 1 at a time, beating well after each addition.
Step #9 At lowish speed, add the dry ingredients in 3 parts, alternating with the wet in 2 parts, beginning & ending with the dry to make a smooth batter.
Step #10 Evenly mound 2 tbsps batter per cookie onto the prepared cookie sheets, spacing them about 2-inches apart.
Step #11 (A small cookie scoop or ice cream scoop is ideal for this.
Step #12 ) Bake until the cookies are golden brown around the edges, 12 to 15 mins.
Step #13 Transfer cookies to rack & cool completely.
Step #14 For the chocolate icing: Put the chocolate in a medium heatproof bowl.
Step #15 Bring the cream to a boil in a small saucepan; pour over the chocolate.
Step #16 Shake the bowl carefully so cream settles around the chocolate; set aside until the chocolate melts, about 5 mins.
Step #17 Whisk until smooth, taking care not to incorporate too many air bubbles.
Step #18 Fill a pastry bag fitted with a small tip with about half of the chocolate icing.
Step #19 For the white icing: Whisk the confectioners' sugar, corn syrup, lemon juice & warm water together to make a smooth icing.
Step #20 Fill a pastry bag fitted with a small tip with about a quarter of the icing.
Step #21 To Decorate:
For tuxedo cookies: Set the cookies on a rack over a rimmed cookie sheet.
Step #22 Pour the white glaze over the whole cookie to cover; set aside to dry.
Step #23 Pipe a bowtie & tuxedo lapel with the chocolate icing.
Step #24 For a little black dress & pearls: Pipe an outline of a woman's dress with the dark chocolate & fill in with more icing.
Step #25 Pipe white icing pearls around the top of the cookie.
Step #26 Add silver dragees or candy pearls to dress up, if desired.
Step #27 Let cookies dry completely, about 20 mins.