Crumble the biscuits in a bowl into a sand-like consistency. Add cocoa, sugar, walnuts and pour the melted butter in. Mix, until you get a batter. If it is too dry, you can add more butter. Shape the mixture into figures like small rocks.
Arrange them on a plate and leave for 20 minutes in the refrigerator to solidify. Meanwhile, melt the chocolate in a water bath or in the microwave. I used dark chocolate, but you can use milk chocolate too.
Immerse the tips of the chilled small rocks in chocolate, sprinkle with coconut flakes and leave in the fridge for another 10 minutes.