Wow! This is a great drink! I found this recipe at https://kitchenswagger.com/blackberry-bourbon-smash-recipe/ which I stumbled across via a Pinterest search.
I modified the recipe slightly. I really recommend checking out the link above – his pics are way better than mine!
Ingredients:
4 blackberries
6-7 mint leaves
1/2 ounce lime juice
2 ounces bourbon
1/2 ounce simple syrup
1 ounce club syrup
Directions:
In a cocktail shaker, muddle the blackberries, mint and lime juice. Add the bourbon and simple syrup. Fill the shaker with ice and shake well. Use the cocktail strainer and pour into a glass filled with ice. Top with one ounce of club soda.