Heat oven to 350°F with rack set in middle position. Line baking sheets with parchment paper.
Whisk together flour, cocoa powder, baking soda, baking powder, and salt in a bowl; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream butter, granulated sugar, and brown sugar at medium-high speed until light and fluffy; scraping down sides of the bowl as needed.
Add eggs and vanilla and beat at medium speed until combined.
Add half of the flour mixture to mixer and beat at low speed until nearly combined, add remaining flour mixture and mix until just combined.
Add chocolate, raspberries, and millet to dough and mix just to combine.
Working with 3 tablespoons (#20 scoop) of dough at a time, scoop dough onto prepared baking sheets set 2-inches apart.
Bake 1 sheet at a time until edges are just set and centers are slightly puffed and cracked, 12–14 minutes, rotating sheet halfway through baking.
Let cookies cool on baking sheet 5 minutes then transfer to wire rack to cool completely.