Watermelon Lassi Cocktail

Name: Watermelon Lassi Cocktail
Prep time: 10 min
Total time: 10 min
Cuisine: Indian
Ingredients: 3 oz white rum; 1½ cup watermelon ((roughly chopped) - use sweet watermelon and chill it for a few hours before blending.); 1 oz simple syrup ((optional) - see notes); 1 cup yogurt ((use straight from the refrigerator)); ½ tsp ground cardamom; ¼ tsp ground pepper; Watermelon balls and mint leaves for garnish