Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper.

In a medium saucepan, melt the 1 cup of cubed butter and 8 oz of chopped semi-sweet chocolate over low heat, stirring constantly until smooth. Remove from heat and let cool for 5-10 minutes.

Pour the melted chocolate mixture into a large bowl. Whisk in the granulated sugar and brown sugar until combined.

Add the eggs one at a time, whisking vigorously for 30-45 seconds after each addition. Whisk in the vanilla extract. The mixture should become thick, glossy, and smooth.

In a separate medium bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and fine sea salt.

Gently fold the dry ingredients into the wet chocolate mixture using a spatula until just combined (a few flour streaks remaining is okay).

Fold in the 2 cups of chocolate chips until just distributed. Do not overmix.

Let the cookie dough rest at room temperature for 10-15 minutes to firm up slightly. The dough will be very soft and batter-like.

Drop rounded tablespoons (about 1.5-2 tbsp each) of dough onto the prepared baking sheets, spacing them about 2-3 inches apart.

Sprinkle the top of each cookie dough mound generously with flaky sea salt.

Bake for 10-12 minutes. The cookies should be set around the edges with crinkly tops, but still very soft in the center. Do not overbake.

Let the cookies cool on the baking sheets for 10 minutes before transferring them to a wire rack to cool completely. They will firm up as they cool.