Preheat oven to 350ºF and line two cookie sheets with parchment or silpat liners.
In a medium bowl, combine the flour, baking soda, and salt. Sift cocoa and add to flour mixture. (I like to use a fine-mesh strainer and sift the cocoa right over the bowl with the flour.) Set aside.
In a large mixing bowl, cream together the butter and sugars until light and fluffy. Add eggs and vanilla and mix until well combined.
Stir in flour mixture until just combined. Mix in Peppermint Crunch chips and white chocolate chips.
Using a medium cookie scoop, drop onto prepared baking sheets.
Bake for 9-11 minutes. Cookies will still be soft in the middle. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
Notes
High altitude changes: I reduced the granulated sugar to ¾ cup, add 1 tablespoon flour, and decreased the baking soda to 1 ½ teaspoons.