First, you need to turn your fresh watermelon into a smooth liquid base. Take your watermelon cubes and place them into a blender. Blend on high until the mixture is completely smooth. To ensure a silky texture, pour the puree through a fine-mesh strainer into a bowl to remove any remaining pulp or seed fragments. This step guarantees your mojito is smooth and easy to drink.
Next, it's time to release the essential flavors of the mint and lime. In each of your two tall glasses, add 6-8 fresh mint leaves and a couple of lime wedges. Using a muddler or the back of a wooden spoon, gently press down and twist a few times. The goal is to bruise the mint leaves to release their fragrant oils, not to tear them into tiny pieces.
Now you can build the foundation of your mojito. Pour 2 ounces of white rum and 1 ounce of simple syrup into each glass directly over the muddled mint and lime. Give it a gentle stir to combine the rum and syrup with the fresh mint and lime juice you just released. This creates the sweet and boozy base for your cocktail.
It's time to bring in the star of the show. Divide your freshly made watermelon puree evenly between the two glasses. Stir everything together once more to fully incorporate the watermelon flavor. Next, fill each glass to the top with ice. Crushed ice is ideal for that classic mojito look and feel, but regular ice cubes will also keep your drink perfectly chilled.
For the final touch, top off each glass with club soda to add that essential fizziness. Give the drink one last light stir to mix everything without losing the bubbles. Garnish with a fresh sprig of mint and a small watermelon wedge on the rim of the glass. Serve immediately and enjoy the ultimate taste of summer refreshment.