Preheat your oven to 325°F (163°C) and line a 17x12-inch baking pan with parchment paper, greasing it lightly.

In a medium saucepan over low heat, combine bittersweet chocolate and unsalted butter, stirring until smooth.

In a large mixing bowl, whisk together the large eggs, granulated sugar, and light brown sugar until pale and thickened.

Pour the warm melted chocolate and butter mixture into the egg and sugar mixture and stir until fully combined.

In a separate bowl, whisk together all-purpose flour, cocoa powder, and salt, then gently fold into the chocolate batter.

Spread brownie batter into the prepared pan and sprinkle dark chocolate chips on top.

Bake for 25-30 minutes or until the tops are shiny with cracks forming.

Remove from oven and cool in the pan for 15 minutes. Lift out using parchment and cool completely before slicing.