Preheat your oven to 350°F (175°C).
Grease a 9x13-inch baking pan with butter or cooking spray.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the eggs one at a time, then add the vanilla extract.
Gradually add the dry ingredients to the wet mixture and stir until just combined.
Fold in the white chocolate chips and crushed peppermint candies.
Spread the batter evenly into the prepared baking pan and bake for 25-30 minutes.
Allow the cookie bars to cool in the pan for at least 15 minutes before cutting into squares.