In a small saucepan, bring the cream to the boil. Remove from the heat and pour over the chopped chocolate. Gently stir the mixture until smooth, then add the alcohol or vanilla extract and hazelnuts. Cover and put in the fridge for 30 mins or until the mixture is thick but not solid.
Scoop out teaspoons of the mixture and roll into small balls with your hands. Put each of your sprinkles or glitters onto separate small plates or bowls. Roll each truffle into the sprinkles or glitter to coat, then chill again to firm up. Will keep chilled for 1 week, or freeze for up to 1 month without the decoration.