Pop the popcorn, as previously described, just before it is required. Break the chocolate into a small bowl or saucepan along with the butter and golden syrup. Heat the mixture on a low heat or in the microwave until the chocolate has melted. Remove from the heat, add the chopped mixed nuts and stir the contents together to form a smooth, glossy mixture. Pour the mixture over the freshly popped corn and mix together, ensuring the popcorn is evenly coated. Allow the mixture to cool before eating.