Preheat the oven to 170 degrees Celsius.
Line the brownie pan with baking paper/wax paper to avoid the brownie from sticking to the pan. Make sure to leave an overhang of baking paper on either side – this makes it easy to lift the brownies from the pan.
Melt the chocolate and butter in a microwave-safe bowl or over a double boiler until both ingredients are fully melted and combined.
Add the white and brown sugar to the chocolate mix and stir it with a whisk until combined while it’s still hot.* Make sure to mix it for at least 3-5 minutes (PS: the sugar will not dissolve completely, so don’t worry if the batter looks grainy at this point)
Once the sugar is combined, add the eggs and vanilla extract, and whisk it again until the eggs are well incorporated into the chocolate batter.
Add the sifted cocoa powder, all-purpose flour, and salt and fold them into the chocolate batter using a spatula or a wooden spoon. This takes some time and energy, so be patient while you’re doing it. There should be no streaks of flour left in the batter by the time you’re done mixing it all in
In the prepared baking pan, add a very thin layer of the brownie batter at the bottom to help the biscuits stay in place. Place a layer of biscuits at the bottom, then top it with the remaining batter.
Bake the brownies for about 30-40 minutes, until the brownies are cooked but still fudgy.* Once your top looks set and the test toothpick has some crumbs, your brownie is ready
Take out your brownies and let them cool completely.
Optional: Top the cooled brownies and top them with melted chocolate before slicing them.