In a medium bowl, whisk together 2 cups of all-purpose flour, 3/4 cup of cocoa powder, 1 teaspoon of baking powder, 1 teaspoon of baking soda, and 1/2 teaspoon of salt until thoroughly combined.

Using an electric mixer, beat together 1 cup of softened unsalted butter, 1 cup of packed brown sugar, and 1/2 cup of granulated sugar until creamy and smooth.

Mix in 6 ounces of melted dark chocolate until fully combined, then add 1 large egg and 2 teaspoons of vanilla extract.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined.

Fold in 1 1/4 cups of chocolate chips until evenly distributed throughout the dough.

Cover the bowl with plastic wrap and refrigerate the cookie dough for at least 3 hours, ideally up to 48 hours.

Preheat your oven to 350°F (180°C) and form cookie balls with 3-4 tablespoons of dough, placing them on parchment-lined baking sheets.

Bake for 12-14 minutes, watching for the edges to set while the centers remain slightly soft.

Let the cookies cool on the baking sheets for about 10 minutes before transferring to a wire rack.