Swirl the chocolate syrup around in a glass all fancy-like. Place the ice cream on the bottom and pour the cold stout slowly into the glass. Top with whipped cream, crushed chocolate candies and Jacked Cherries if using. Serve with a straw, a long spoon and a shot of whisky, if desired.
Bring the whisky and sugar to a gentle simmer in a small saucepan and simmer until the sugar is dissolved. Pour the mixture over the cherries in a mason jar and let it sit in the fridge overnight.