In a cocktail shaker, add basil leaves, peach nectar, and lemon juice. Muddle basil lightly with a drink muddler or the end of a wooden spoon.
Add honey, lemongrass paste, bourbon and fill shaker 1/2 way with ice. Cover and shake vigorously for 30 seconds to chill drink.
Strain into highball glass filled with fresh ice. Top with club soda, if desired. Garnish with more fresh basil leaves, if desired, and serve immediately.