Start by melting butter and chocolate together until it reaches a completely liquid consistency.
Let it stand and cool while the rest is prepared.
Whisk the eggs thoroughly with a whisk until they become slightly creamy in consistency.
Then gradually add sugar while continuing to whisk.
Once it has a completely creamy consistency, mix in the chocolate mixture and whisk again.
Now mix flour, cocoa, and vanilla sugar together and add it to the mixture.
Finally, add chopped peanuts.
Line a baking pan with parchment paper and pour the cake batter into it.
Bake at 190 degrees Celsius (374 degrees Fahrenheit) in a conventional oven for about half an hour.
Optionally test by inserting a fork to see if it is done.