Bitterness balances with sweet in this Campari old fashioned. Rather than add in bitters to the cocktail we use Campari to bring out citrus and bitter to blend with the whiskey. It’s a lovely twist that evolves as the ice melts and the the cocktail dilutes.
For the brown sugar simple syrup, combine 1 cup of light brown sugar to 1 cup of warm water and stir or shake until the sugar dissolves. Store in the fridge for 1 to 2 weeks, longer if you add a smidge of vodka to it.