Peppermint Bark Whoopie Pies

2 c. flour
5 T. cocoa
1 1/8 t. baking powder
1 t. baking soda
½ c. unsalted butter, room temperature
1 c. sugar
2 egg yolks
1 T. vanilla extract
1 c. milk
15 scoops Blue Bell Peppermint Bark Ice Cream, approximately ½ cup each

Preheat oven to 375°F.  Line 2 large baking sheets with parchment paper.  Combine flour, cocoa, baking powder and baking soda in a medium bowl.  Beat butter, sugar, egg yolks and vanilla in a large bowl until well blended, about two minutes.  Add flour mixture in three additions alternately with milk in two additions, beating until blended after each addition.  Drop dough by very rounded tablespoonfuls onto prepared baking sheets, spacing three inches apart.  Bake one sheet at a time until cookies are slightly puffed and spread but are still soft, 8 to 10 minutes.  Cool on sheets ten minutes.  Carefully transfer cookies to racks and cool completely.  Repeat with remaining cookie dough.  Cookies can be made one day ahead.  Store airtight in single layer at room temperature.  When ready to serve, place one cookie flat-side up.  Add a scoop of ice cream.  Top with a second cookie, flat-side down.  Press gently to spread the ice cream to the edge of the cookie. Make one sandwich for each serving.  Serve immediately.  Makes about 15 sandwiches.