Melt the Chocolate and Butter:
In a heatproof bowl, melt the butter and chopped chocolate together in the microwave in 30-second increments, stirring in between, until smooth. Let cool slightly.
Combine the Dry Ingredients:
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.
Mix the Wet Ingredients:
In a large bowl, beat the eggs, sugar, and vanilla extract until light and fluffy, about 2-3 minutes. Slowly add the melted chocolate mixture and mix until well combined.
Incorporate the Dry Ingredients:
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Chill the Dough:
Cover the bowl with plastic wrap and chill the dough for at least 30 minutes to 1 hour. This helps prevent the cookies from spreading too much during baking.
Preheat the Oven:
Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat.
Shape the Cookies:
Using a cookie scoop or tablespoon, portion out the dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake the Cookies:
Bake for 10-12 minutes, or until the tops are crinkly and set. The centers will still be soft.
Add Sea Salt:
Immediately sprinkle the tops with a pinch of sea salt flakes while the cookies are warm.
Cool and Serve:
Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.