Preheat the oven to 180°C / 350°F / gas 4. Prepare your lined tin - I use a 20.5 x 30.5cm one. Put the butter in a heatproof bowl along with the dark chocolate. Place a small amount of boiling water into a saucepan and rest the heatproof bowl with the butter and chocolate on top, then melt the contents on a low heat. You don't want the water to boil. Once melted set aside.
Add the sugar and eggs to your electric mixer then whisk for about two minutes until your mixture is slightly frothy.
Pour the chocolate mixture into the bowl and whisk in for a few minutes until all of your mixture is all combined.
Sift the flour and cocoa powder into your mixture and stir with a wooden spoon until your mixture is all combined.
Add half your mixture to your prepared tin, pouring it in evenly. Gently bang the tin on the work surface to get rid of any air bubbles.
Now for the caramel. Place the sugar into a saucepan and place over a medium heat and leave it alone without stirring.
Keep a close eye on it until the sugar begins to melt and turn to liquid. This will first happen around the edges. It should take about 3-5 minutes, don't be tempted to stir it - you must leave it!
When it has started to melt more around the edges give the saucepan a good shake. Leave it on the heat until about a quarter of the sugar has melted.
Now using a wooden spoon gently stir until all the sugar crystals have all melted into a liquid.
Continue to cook, stirring now and then until the sugar has turned to a dark colour, like honey.
Take the pan off heat and add the water. Be extremely careful as it's very hot and it may splutter a bit.
Put it back on a low heat and add the cream. Keep stirring. If lumps appear keep stirring until melted. Add the salt, stir then take off the heat and allow to cool for a minute.
Add your caramel to the top of your brownie mixture, making sure you get an even layer. Then add the rest of your brownie mixture on top. Gently bang the tin again to release any more air bubbles.
Carefully place them in the oven for 20 minutes. To test the brownies are cooked put a metal skewer in and it should come out clean.
Leave the brownies to cool for about 5 minutes and push the fudge pieces in to the brownies. Leave to cool for about 20 minutes then put them into the fridge for about an hour before cutting up in to squares. Simply have them on their own or with some vanilla ice cream. These brownies ideally need to be eaten with a fork! Enjoy!