Pre-heat your oven to 200C/180C Fan/Gas Mark 6. Line an 8" Square Pan with greaseproof paper.
In a small bowl, break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn't burn. Set aside to cool.
In a large mixing bowl, whisk together melted butter and both sugars. With an electric/stand mixer, go for a solid 3-5minutes so it is totally combined. Add in the eggs and mix again.
Add the melted dark chocolate slowly (check it first, to make sure it isn't so hot that it will cook the eggs) and combine once again.
Gently fold in the flour and cocoa powder, along with the various chopped Kinder Chocolate. Save a little for decoration after baking.
Pour the batter into the lined pan and bake approx 25-30 minutes. Remove pan from oven once cooked, feel free to add a few more of those chopped chocolate chunks - so they melt a little. Once cool, slice and serve!