In a mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
In a separate mixing bowl, whisk together the eggs, sugar, vanilla and melted butter.
Add the wet ingredients to the flour mixture and fold together with a spatula. Stir in the chocolate chips. Pour ½ of the brownie batter into a 9x13 baking dish that is lined with parchment paper, and spread evenly.
Unwrap and roughly chop 10 of the peppermint bark candies. Sprinkle the chopped peppermint bark over the batter then pour the remaining brownie batter over the bark. Spread evenly.
Bake at 350 degrees for 20-25 minutes until the center is fudge-like but not dry. Remove from the oven and cool for 10 minutes.
Unwrap and chop the remaining candies. Place the Peppermint Bark chunks on top of the warm brownies and allow to soften for 1 minute. Use a spatula to gently swirl the melting bark. Refrigerate for 1 hour.
Lift the sides of the parchment paper to remove the brownies from the pan. Use a sharp knife to trim the edges, then cut into 18 squares.