Melt 1/2 cup sugar with 3 tablespoons water in a saucepan over medium-low heat, occasionally swirling the pan, until the sugar starts to bubble and turn golden brown, about 7 minutes. Remove from the heat and divide the syrup among 8 (1/2) cup ramekins so the bottoms and sides are covered with the syrup. Preheat the oven to 275 degrees. Meanwhile, whisk the remaining sugar, coconut milk, whole milk, and eggs in a bowl until the sugar is completely dissolved. Divide the mixture among the ramekins. Create a water bath by filling a baking dish halfway with water. Place the ramekins in it and bake until the custards set, about 35 minutes. Remove from the oven and allow to cool in the water bath. Cover with plastic wrap and refrigerate and least 12 hours. To serve, loosen the sides with a knife and invert custard onto plates so the caramel is on top, drizzling any remaining caramel on the plates around the custard. Serve chilled garnished with a mint leaf.