Preheat your oven: Set your oven to 350°F (175°C). Grease a 9x9 inch (23x23 cm) baking pan with butter or line it with parchment paper for easy removal later.
Melt the chocolate and butter: In a medium saucepan over low heat, combine the chopped dark chocolate and butter pieces. Stir continuously until both are completely melted and combined into a smooth mixture. Remove from heat and let it cool for about 5 minutes.
Prepare the egg mixture: In a large mixing bowl, whisk together the granulated sugar, room temperature eggs, and pure vanilla extract until everything is well blended and slightly frothy.
Combine chocolate and egg mixtures: Gradually pour the cooled chocolate-butter mixture into the egg mixture. Whisk constantly until the mixture becomes glossy and rich in color.
Mix dry ingredients: In a separate bowl, sift together the all-purpose flour, cocoa powder, baking powder, and fine sea salt to ensure there are no lumps.
Incorporate dry ingredients: With a spatula, gently fold the dry ingredients into the chocolate-egg mixture until just combined. Take care not to overmix; it’s okay if a few small streaks of flour remain.
Add orange zest and chocolate chips: Gently fold in the orange zest and chocolate chips (if using) until evenly distributed throughout the batter.
Transfer batter to pan: Pour the brownie batter into the prepared baking pan, using a spatula to smooth the top for even baking.
Bake the brownies: Place the pan in the preheated oven and bake for 25-30 minutes. Check for doneness by inserting a toothpick into the center; it should come out with a few moist crumbs attached, but not wet batter.
Cool and transfer: Remove the brownies from the oven and let them cool in the pan for about 10 minutes. After cooling slightly, transfer the brownies to a wire rack to cool completely.
Cut and serve: Once the brownies have cooled entirely, cut them into generous squares. For an extra touch of indulgence, lightly dust the tops with powdered sugar before serving.
Notes
For an extra touch of indulgence, lightly dust the tops with powdered sugar before serving.