Preheat oven to 325°F. Line two cookie sheets with parchment paper.

In a medium microwave-safe bowl, add 1 cup of the semi-sweet chocolate chunks and the butter. Heat in the microwave for 15 seconds. Stir and then heat for another 15 seconds. Stir. If the chocolate is mostly melted do not heat again.

While the chocolate is cooling, add granulated sugar, eggs, whole milk, and vanilla extract to a large bowl. Whisk well until they are completely incorporated, light, and airy.

Add the slightly warm melted chocolate to the egg mixture and whisk continuously until fully combined and smooth.

In a separate bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, and kosher salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Fold in the remaining chocolate chunks.

Drop rounded spoonfuls of dough onto the prepared baking sheets, leaving space between them. Bake for 10-12 minutes, or until edges are set but centers are still soft. Let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.