To make the mint simple syrup: Bring the water to a boil in a small saucepan. Remove from the heat and add the mint leaves. Lightly press the leaves against the side/bottom of the pot to release the oils into the water. Let sit and cool for at least 30 minutes.
In a cocktail shaker, add the bourbon, tequila, lime juice and mint syrup. Pour over a rocks glass with the crushed ice. Top with a lime wedge and mint sprig.