Mix all ingredients in a 6 ounce cocktail glass over ice. Stir to combine. Taste for sweetness and add more blueberry simple syrup to your preference. Garnish with a mint leaf.
for the blueberry simple syrup
In a small saucepan, bring all simple syrup ingredients to a simmer and cook over medium low until jammy. This will take 20-30 minutes, stirring occasionally.