How to Make It
Sift together flour, baking powder, salt, and baking soda in a medium bowl. Set aside.
Beat together butter, granulated sugar, and brown sugar with a stand mixer at medium-high speed until light and fluffy, about 5 minutes. Add eggs, 1 at a time, beating to incorporate. After adding both eggs, continue to beat until very whipped, 3 to 4 minutes. Add vanilla.
Reduce speed to low, and gradually add flour mixture to butter mixture; beat until combined, about 10 seconds. Fold in peppermint bark pieces.
Scoop cookies with a 2-inch scoop about 2 inches apart onto a baking sheet lined with parchment paper. Cover baking sheets with plastic wrap, and chill at least 24 hours, and up to 48 hours (or alternatively, don’t cover and freeze until firm, about 15 minutes).
Preheat a convection oven to 425°F (or a conventional oven to 450°F). Bake cookies in preheated oven until puffed and golden, 7 to 8 minutes. Let cookies stand about 5 minutes before transferring to a wire rack.