Combine bourbon, Sage liqueur, grapefruit juice, lime juice, agave, and bitters in a cocktail shaker. Fill shaker with ice and shake until outside is frosty, about 30 seconds; strain into a coupe glass. Slap sage leaf between your palms until fragrant; float on top of cocktail.
Recipe by Allons-Eat! at https://www.allonseat.com/sage-brown-derby-cocktail/