How to make
Crumble the biscuits in a blender. To them, add the walnuts and blend. Pour the mixture into a bowl, add the cocoa and powdered sugar.
Melt the butter and add it to the bowl as well. Stir everything well. Form rocks from the mixture and arrange them in an oven dish covered with baking paper.
Melt the chocolate in a water bath and pour it over the rocks. Sprinkle with coconut flakes.