Add granulated sugar, water, and half habanero pepper to a saucepan.
Cook on low until the sugar is dissolved, stirring frequently.
Remove the pan from the heat and let the habanero steep for 15 minutes. Strain the mixture using a fine sieve into a lidded jar. Store in the fridge until ready for use. You will get ¾ cup of simple syrup which is good to make 4-5 servings of this drink.
Mix together 1 teaspoon red chili powder and 1 teaspoon salt on a small plate. Wet the rim of 2 margarita glasses by rubbing a lime wedge along the rim and then dip the rim in the chili powder/salt mixture.
Place 1 cup cubed mangoes and 3 oz (90 ml) habanero simple syrup in the jar of a high powdered blender.
Blend until smooth.
Fill a shaker with 3-4 ice cubes (don’t use too many, as the margarita ingredients fill the shaker most of the way).
Pour in the mango mixture, 4 and ½ oz (135 ml) tequila, 1 and ½ oz (45 ml) grand marnier, and 3 oz (90 ml) lime juice.
Shake until chilled.
Strain evenly into the prepared glasses.
Add a few ice cubes to each glass, garnish with mint leaves and serve immediately!