Black-and-White Whoopie Pies

Cookies: Place oven racks in upper and lower third of oven. Heat oven to 350 °F. Line 4 baking sheets with parchment. Whisk flour, baking powder, baking soda, and salt in a medium bowl. Beat butter and granulated sugar in a large mixer bowl on medium speed until light and fluffy, about 2 minutes. Add eggs and vanilla until blended. Add flour mixture in three additions alternately with milk, beginning and ending with the flour. Beat until just combined. Divide dough in half and add chocolate to one half, stirring until just blended. Use a scant 1/4 cup ice cream scoop to drop chocolate dough 3 inches apart on 2 baking sheets. Bake 12 to 13 minutes, or until centers are soft but firm and edges are just beginning to brown. Cool 5 minutes. Transfer to a wire rack to cool completely before filling. Repeat with vanilla dough using a full 1/4 cup scoop. Filling: Beat marshmallow cream, butter, vanilla, and confectioners' sugar in a large mixer bowl until light and fluffy. Fold chocolate into 1 cup of the filling. Spoon 3 Tbsp of chocolate filling onto center of six white cookies. Top each with remaining white cookies. Repeat with chocolate cookies, using vanilla filling. Lightly dust with confectioners' sugar, if desired.