Pour the bourbon into a shaker (or clean jar with a lid), add the jam and stir to dissolve.
Add all the other ingredients, giving the mint leaves a good slap first, to wake them up.
Shake hard to get a good foam going (this is known as a dry shake), then add a big handful of ice and shake again (a wet shake).
Strain into a coupe glass and garnish with a mint leaf; when blackberries are in season, I like to pop one on top, too.
