Preheat the oven to 350℉. Line two baking sheets (12'x17") with parchment paper. Set aside.
In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt to distribute everything evenly together. Set aside.
2 cups all-purpose flour, ¾ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon kosher salt OR sea salt
Using either a large mixing bowl with an electric hand mixer, or a stand mixer with the paddle attachment, cream together the butter, granulated sugar, and light brown sugar until light & fluffy and paler in color. About 2-3 minutes.
1/2 cup (1 stick) butter, 1/2 cup granulated sugar, 1/2 cup packed light brown sugar
Add the egg, vanilla extract, and peppermint extract. Mix on low speed just until everything is incorporated. Nothing more as you don't want to overbeat the eggs.
1 large egg, 1 teaspoon vanilla extract, ¼ teaspoon peppermint extract
Add in the dry ingredients (set aside from earlier) and beat on low speed just until combined and a cookie dough forms.
Add in the white chocolate chips and crushed candy canes. Mix on low speed just until incorporated.
3/4 cup white chocolate chips, 1/4 cup finely crushed peppermint candy canes
Put the crushed candy canes (for the tops of the cookies) into a small bowl.
1/4 cup finely crushed peppermint candy canes
Use a medium cookie scoop (1.5 tablespoons) to scoop the cookie dough out and then roll it into a ball. Dip the top of each cookie dough ball in the crushed candy canes. Place 12 cookies per cookie sheet.
Bake for 8-10 minutes or until the edges are set and barely starting to turn golden brown.
Remove the cookies from the oven and let them cool on the warm cookie sheet for about 20 minutes before removing them to a cooling rack to cool completely.