1. Preheat the oven to 350°F and line 2 baking sheets with parchment paper.

2. Melt the 1 cup semi-sweet chocolate chips with the butter in a microwave-safe bowl in 20-second bursts, stirring until smooth. Let it cool for 5 minutes.

3. In a large bowl, whisk the granulated sugar, brown sugar, eggs, and vanilla extract until smooth and slightly thickened.

4. Pour the melted chocolate mixture into the egg mixture and whisk until glossy.

5. In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.

6. Fold the dry ingredients into the wet mixture just until combined.

7. Fold in the 1/2 cup chocolate chips or chunks.

8. Let the batter sit for 10 to 15 minutes if it feels too loose.

9. Scoop mounds of batter onto the prepared baking sheets, leaving space between each cookie.

10. Bake for 10 to 12 minutes, until the tops are crackly and the edges are set.

11. Sprinkle with flaky sea salt if using.

12. Cool on the baking sheet for 10 minutes, then transfer to a wire rack.