Choose a ripe mango that yields slightly to gentle pressure and smells sweet at the stem end. Peel, pit, and cut the mango flesh into chunks.

Add your mango chunks to a blender and pulse until completely smooth, about 30 seconds. Push the puree through a fine mesh strainer if you prefer a silkier texture without any pulp.

Roll a fresh lime firmly on the counter to break down the internal membranes. Cut it in half and squeeze by hand or with a citrus juicer until you have at least 0.75 ounces of fresh juice.

Using a jigger, accurately measure out 2 ounces of white rum, 1.5 ounces of mango puree, 0.75 ounces of fresh lime juice, and 0.5 ounces of simple syrup.

Add about 1 cup of ice cubes to your cocktail shaker until it's roughly three-quarters full.

Pour the rum, mango puree, lime juice, and simple syrup into your shaker with the ice.

Seal your shaker and shake hard and fast for about 10 to 12 seconds until the outside of the shaker becomes frosty and ice sounds like it's moving rapidly inside.

Place a strainer over your cocktail glass and pour the mixture in smoothly, letting the ice stay behind in the shaker. Add fresh ice to the glass if you prefer a longer drink, or serve it as-is for a more concentrated flavor.

Top with a thin slice of fresh mango or a lime wheel, then serve immediately while the drink is still ice-cold.