Blend peeled, chopped mango until smooth. (Or mash very well with a fork). Set aside 2 oz puree.
Place mint leaves and fresh lime juice in a strong glass.
Press mint gently 3-4 times with a muddler to release oils. Do not shred the leaves.
Add 2 oz mango puree and the simple syrup to the glass.
Fill the glass almost completely full with ice cubes.
Pour chilled club soda over the ice until the glass is full.
Use a long spoon to stir carefully from the bottom up, mixing without losing fizz.
Garnish with a fresh mint sprig and a lime wedge. Serve immediately.