I have a cough. I think mine is linked to acid reflux. I dont always have heartburn, but I have noticed that I cough some time after eating. It's a nuisance more than anything else. You've made me wonder about chocolate now. I think I might start a cough diary and see if there is a correlation.
I have the same problem which happens more at this time of the year. Put it down to hay fever making my throat sensitive and take hayfever tablets which help no end. I cleared Waitrose yesterday when I suddenly had a fitting cough near the flowers, luckily jjI had my mask on.
If you have acid reflux it could be a possible hiatus hernia, where the diaphragm sphincter doesn't close properly and allows acid to escape into the oesophagus. Chocolate relaxes the sphincter even more and allows more acid to escape. A cough is one of the side effects of hiatus hernia.