Preheat the oven to 180 degrees Celsius (350 Fahrenheit).
In a pan set over a low to medium heat, add the dark brown sugar, butter cut into cubes, and chocolate broken into pieces.
Use a rubber spatula to stir everything well to melt into a smooth mixture.
Leave the mixture to cool down.
In a large mixing bowl, add the granulated sugar and eggs, and use a hand mixture to beat them well until they triple their volume and you get mixture that is light and has a pale yellow colour.
Sift in the flour and cocoa powder, add the chocolate mixture, and mix to get a smooth batter.
Line a square baking tray with non-stick paper (mine is 24 cm x 5 cm or 9 inches large and 2 inches high), and add half of the chocolate mixture, spreading it well.
Top it a layer of caramel, then the remaining chocolate mixture.
Use a popsicle stick to swirl the mixture, then bake for 35 minutes.
Remove the tray from the oven and leave the brownies to cool down completely in the tray.