Muddle mint leaves with orgeat. Add everything else, then shake with ice and strain into a chilled rocks glass filled with ice. Top with 1 oz. Club Soda. Garnish with a mint sprig.
I named this Southside Fizz variation after the three parks (Madison Square to the north, Gramercy to the east, and Union Square to the south) in Gramercy Tavern's neighborhood. —Jim Meehan, New York, 2005