Put into the basin the ground almonds, icing sugar and chocolate powder. Put the egg yolk into a cup, add a few drops of evaporated milk, beat together, then add a few drops of vanilla essence or ½ teaspoon of coffee essence. Pour this into your basin of mixture and using your hands, mix into a soft dough. Leave this to get very cold – you could put it into the fridge for half an hour.
Sprinkle a large sheet of greaseproof paper with a little more chocolate powder, or chocolate vermicelli is better to use if you have any; shape the mixture into small balls and roll them in the powder or vermicelli. If you have any paper cases, put the truffles into them.