In a large bowl, cream together butter and sugar. Add egg and vanilla and mix until well combined. Add baking soda, powder, salt and ⅔ cup of flour.
Divide the dough in half (about 180 g of dough per bowl) and place half in a second bowl.
To the first bowl of the dough, add the additional flour and the chocolate chips. To the second bowl of dough, add the cocoa powder and the white chocolate chips. The dough will be a bit sticky. Chill for 1 hour.
Preheat the oven to 350 °F. Remove the cookie dough from the refrigerator. Divide the two types of dough into 24 balls each (about 1-1.5 tablespoon per ball). Squish a cookie dough ball of each type together and place on a prepared cookie sheet.
Bake for 10-13 minutes until lightly browned on the edges. The centers will still look a bit soft. Remove cookie sheet from the oven and allow cookies to cool on the pan for 5 minutes. After 5 minutes, move cookies onto a rack to finish cooling.
Notes
LeftoversStore leftovers in an airtight container at room temperature for up to 5 days or freeze for up to 3 months.