Preheat oven to 180 degrees celsius.
Line 2 flat cookie baking trays with baking paper and set aside.
Place the chopped butter and chocolate melts into the TM bowl.
Melt on Speed 2, 80 degrees for 3 minutes (or until melted) - you may need to scrape down the bowl partway through.
Remove melted chocolate/butter and set aside.
Place the eggs, caster sugar, cocoa powder and vanilla extract into the TM bowl (no need to clean it).
Insert the butterfly and mix on Speed 4 for 2 minutes.
Reduce to Speed 1 and slowly add the melted chocolate mixture to the egg mixture through the MC hole.
Increase to Speed 3 for 20 seconds.
Redue to Speed 1 and add the salt, baking powder and plain flour through the MC hole.
Mix until just combined.
Add the white chocolate chips/peanuts (or whatever add-ins you like) and fold through with a spatula.
At this stage the mixture will be very thin (almost like a cake batter).
Place tablespoonfuls of the mixture onto the prepared trays.
The cookies will spread so make sure you leave a 3-4cm gap between each cookie.
Bake for 12 minutes.
Remove from the oven and leave on the baking trays for a further 10 minutes (they will continue to cook).
Use a flat spatula to transfer the cookies to a wire rack to cool completely.