Start by adding lime juice, sugar, and water into a medium-sized pot. Bring the mixture to a simmer, then cover it with a lid. Allow it to simmer gently for about 10 minutes. Covering the pot is important, as it prevents too much water from evaporating and keeps the syrup balanced. Once done, pour the syrup into a glass jar and let it cool in the refrigerator.
Take two serving glasses and run a lime wedge around the rim. On a small plate, mix sugar, lime zest, and a pinch of flaky sea salt. Dip the rims of the glasses into this mixture for a sweet and tangy finish. Fill each glass with crushed ice to keep your mojito nice and cold.
In a cocktail shaker or a sturdy glass jar, place the fresh mint leaves. Use a muddler or the back of a wooden spoon to gently press the leaves. The goal is to release the oils and aroma without shredding the mint into small pieces, which can make the drink bitter.
Add white rum, lime wedges, and lime-infused simple syrup into the shaker along with a handful of ice cubes. Close the shaker tightly and shake for about 15 seconds. This helps blend the flavors while chilling the mixture.
Strain the mojito into the prepared glasses. Top each one with a splash of chilled seltzer water for fizz. Garnish with extra lime slices and a sprig of fresh mint for presentation. Your homemade Mint Mojito is ready to enjoy!