Add butter, sugar, brown sugar, salt, baking powder and baking soda to the bowl of a stand mixer; mix on low until combined; beat on medium speed for 1 minute
Beat in egg and vanilla until smooth; stop mixer and add flour and white chocolate chips; mix on low speed until a cookie dough forms, 1 minute
Use a cookie scoop to form cookie dough balls; dip the top half of each ball into the crushed peppermint candies; place the cookies on a baking sheet with parchment paper
Bake the cookies for 10-11 minutes; cookies should look a little bit underdone but will set up as they cool; allow to cool for 10 minutes before removing