Bring 2 cups fresh mint and 1 1/2 cups each sugar and water to a simmer in a saucepan, stirring to dissolve the sugar. Remove from the heat and let steep 1 hour; strain and chill. Combine 3 cups bourbon with 1 to 1 1/2 cups of the mint syrup. Divide among 6 glasses filled with crushed ice; garnish with mint sprigs.
Photograph by Con Poulos