Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the eggs one at a time, adding the vanilla extract, and mix until well combined.
In another bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add this mixture to the wet ingredients, stirring until just combined.
Fold in the white chocolate chips, semi-sweet chocolate chips, and crushed peppermint candies into the cookie dough.
Scoop tablespoon-sized portions of dough and drop them onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Once cool, melt additional white and semi-sweet chocolate in separate bowls. Drizzle the melted chocolates over the cookies and immediately sprinkle with extra crushed peppermint on top for decoration.
Notes
For extra decoration, drizzle with melted chocolate and sprinkle with crushed peppermint.