Use a culinary mandolin to get beautiful, uniform thin slices. Or sharpen your largest chef’s knife.
½ C sugar
4 sprigs mint plus small leaves for garnish
½ t thinly sliced fresh red chili (such as jalapeño or Fresno)
½ vanilla bean, split lengthwise
½ C fresh lime juice
½ 5-lb. melon, peeled, halved, seeded, cut crosswise into 1/4-inch slices
½ t lime zest
Bring sugar and 1/4 cup water to a boil in a small saucepan over medium heat, stirring to dissolve sugar. Add mint sprigs and chili. Scrape in seeds from vanilla bean; add bean. Remove syrup from heat; cover and let steep for 15 minutes for flavors to infuse. Strain syrup through a fine-mesh sieve into a small bowl; stir in lime juice. Syrup can be made 1 week ahead. Keep chilled. Arrange melon slices in a glass baking dish. Pour syrup over melon in baking dish. Cover with plastic wrap and chill for 2 hours to allow flavors to meld. To serve, divide melon slices among plates, over-lapping them decoratively. Garnish with mint leaves and lime zest. Pour remaining syrup in dish into a small pitcher.