Combine the sugar, water, and mint leaves in a small saucepan

Bring it to a boil and stir until the sugar is dissolved.

Reduce the heat to a simmer and cook for another 5 minutes, stirring frequently.

Use a fine-mesh sieve to strain the mint leaves from the syrup

Discard the mint leaves

Let the syrup cool completely

In a serving glass, carefully muddle the mint leaves and blackberries

Add the bourbon to the glass with 2 tbsp of the mint simple syrup

Stir until everything is combined

Add ice and top with 7Up

Garnish with extra mint leaves