In a heavy saucepan, mix together the sugar and water, bring it to boil at high heat. When it reaches a deep-golden brown color, after about 8 minutes, pour into 6 (8-ounce) ramekins. Let cool.
In a medium sauce pan mix the whole milk, half-and-half, sugar, and orange zest. Bring to a boil, and then simmer for 3 minutes. Remove from the heat, cover with plastic wrap, and let it rest for 10 minutes at room temperature.
In a medium-size bowl whisk the eggs. Return the milk mixture to a boil and then remove from heat. Slowly pour 1 cup of the hot milk mixture into the eggs, whisking briskly to temper the eggs. Then add the egg mixture to the milk mixture, mixing thoroughly. Strain the custard into a spouted measuring cup.
Pour mixture into the ramekins with the caramel. Bake in a water bath, covered with foil, in a preheated 325 degree oven for 22 to 25 minutes. Let cool at room temperature.
Remove the flan from the molds by gently loosening the sides with a small knife. Garnish with orange segments and mint leaves.