Grind or crush the biscuits finely and mix them with 1/5 cup (60 g) of crushed walnuts, the cocoa and 2 tablespoons coconut flakes, if desired. In a dish on the stove, melt the butter, milk, liquid chocolate and powdered sugar to taste while stirring.
Remove it from the heat and mix the rum essence in. Pour this mixture slowly over the crushed biscuits and mix well. If necessary, you can add more milk if you get a mixture that is too dry.
Shape small balls with moistened hands and roll them in the remaining chopped walnuts, coconut flakes, cocoa, crushed biscuits.