To the other half of cookie dough base, add in the flour, cocoa powder, baking powder, baking soda, and salt. Use a rubber spatula to fold the mixture together just until a few flour streaks remain.
Chop up the peppermint white chocolate and add it into the chocolate cookie dough. Fold the mixture together just until no flour streaks remain.
Cover both of the dough bowls with plastic wrap and place them into the fridge for 15 minutes.
After the dough has had a quick chill, scoop out 1.5 tbsp. scoops of each of the doughs.
Use a knife or your hands to split each ball of cookie dough in half.
Alternate adding each half ball of flavor to your hand, for a total of four pieces of dough. Roll the dough into a ball, and repeat with the remaining cookie dough. (For more uniform balls of dough, you can gently press each cookie dough ball into a 3 tbsp. cookie scoop after marblign the doughs together).
Cover the dough balls and place them in the fridge to chill for 15 minutes.
Preheat the oven to 350°F / 175°C.
Evenly space out the cookie dough balls on a parchment lined cookie sheet and top them with extra chocolate and white chocolate.
Bake for 12-14 minutes, or until the edges of the cookies start to turn golden brown.
Once the cookies come out of the oven, I recommend "scooting" them. This just means take a bowl, cup, or biscuit cutter that is slightly larger than the cookie, place it on top of the cookie, and swirl the bowl around to make the cookie a little more round.
Let the cookies sit on the hot baking tray for at least 5 minutes before transferring them to a wire rack to cool. Sprinkle with flaky sea salt, serve and enjoy!