A couple of hours before you are going to make the brownie prepare the nutella.

Line a square baking tin with 2 pieces of baking paper. The brownie piece you will use for the brownie, the top piece you will use for the nutella, which will make it easier to lift out of the pan just before you pour in the brownie mixture.

Dollop tablespoons of nutella into the baking tin and put in the freezer until hard. Leave there until you are ready to pour the brownie mixture into the tin.

Preheat the oven to 180º C (fan forced).

Meanwhile to make the brownie mixture, place the butter into a saucepan and put it on a medium heat on the stove top to melt. Break up the Old Gold chocolate and once the butter has started to melt, add the chocolate to the saucepan. Use a spatula to stir frequently. Once the butter has melted turn off the heat and keep stirring until the chocolate has just melted.

Add the brown sugar and using a whisk, mix well. 

Make sure the butter/chocolate mixture is cool enough to add the eggs. If so, go ahead and crack the eggs into the saucepan and use a whisk to combine the eggs with the chocolate mixture.

Dump in the flour and dark chocolate chips/melts. Mix until just combined.

Remove the nutella from the freezer. Remove the top piece of baking paper from the baking tin (with the nutella pieces on them) and set aside on the bench.

Pour the brownie mixture into the cold lined baking tin.

Evenly place the frozen nutella pieces on top of the brownie mixture.

Bake for 40 minutes. Check at 35 minutes. The brownie is ready if it is soft to touch (if you poke your finger in it would leave a depression/hole).

Don't cook until it's firm/hard. The brownie will harden as it cools and if you cook until it's firm you'll break your teeth when eating the brownie.