Add the gingerbread syrup, bourbon, and ground cinnamon to a large pitcher. Stir until the cinnamon is fully blended into the liquid.

Slowly pour the chilled stout beer into the pitcher. Stir gently to combine without creating excess foam.

Let the mixture rest for two minutes so the flavors settle.

Pour into four glasses. Top each serving with a spoonful of whipped cream and place one gingerbread cookie on the rim.