If you don't have ready mango puree, peel and dice 1/2 a ripe mango and puree in a blender until smooth. Measure out 1 ounce for the drink. (Alternatively use store-bought mango nectar.)

Muddle mint and citrus

In a sturdy highball or Collins glass, add the fresh mint leaves (reserve one small sprig for garnish), the 0.75 oz fresh lime juice, and 0.5 oz simple syrup. Gently muddle 6–8 of the mint leaves with a muddler or the back of a spoon just enough to release the oils — avoid shredding the mint too finely to prevent bitterness.

Build the cocktail

Add the 1 oz mango puree and 2 oz Malibu Mango rum to the glass. Fill the glass with crushed ice (about 1 cup). Stir gently with a bar spoon 8–10 times to combine and chill the drink while distributing the mint and mango evenly.

Top and finish

Top the cocktail with 2 oz club soda and give it one gentle stir to integrate the soda without flattening too much carbonation. Taste and, if you prefer brighter acidity, squeeze the reserved lime wedge into the drink and drop it in.

Garnish and serve

Garnish with the reserved mint sprig (slap it once between your palms to release aroma) and a mango slice on the rim. Serve with a straw and enjoy.