In a bowl, bain marie dark chocolate chips and butter until all melted and combine.
Crush vanilla wafer sandwich in a food processor until very smooth. Add chocolate mixture and a pinch of salt. Blend again with food processor until combined.
Take about 1 tbsp chocolate wafer mixture and make a circle shape. Add 1/2 tsp nutella on the center and form into a ball with nutella in the middle. Do it for the rest of the chocolate wafer mixture.
When ready to be served, dusting with cocoa powder.
You can substitute cocoa powder with powdered sugar.