The beauty of this chilled flan dessert reveals itself in the final step: When turned out onto a serving plate, it is automatically glazed and sauced with the caramel in the mold.
Make the caramel: Prepare an ice-water bath; set aside. Divide sugar evenly between two 4-cup charlotte molds; add 2 tablespoons water to each and swirl to combine (do not stir). Place molds over low heat; cover, and cook until sugar has dissolved.
Uncover molds and increase heat to high; cook, swirling, until sugar mixture begins to caramelize. Remove from heat and immediately plunge molds into ice-water baths to stop cooking, about 30 seconds. Swirl caramel to evenly cover bottom of molds; set aside.
Preheat oven to 325 degrees.
Make the custard: Place cream, milk, and vanilla bean and seeds or extract in a medium saucepan and heat over medium heat for 5 minutes.
Meanwhile, in a large bowl, whisk sugar with eggs and egg yolks until light and fluffy. Remove vanilla bean from milk mixture; whisking constantly, gradually add milk mixture to egg mixture. Strain and divide custard evenly between both charlotte molds.
Place charlotte molds in a roasting pan. Add enough boiling water to come halfway up the sides of the molds. Transfer pan to oven and bake until custard is firm, about 45 minutes. Remove custards from pan and let cool; transfer to refrigerator until chilled.
To unmold, run a sharp knife or offset spatula around the edge of the custard; dip mold into hot water to help remove if necessary. Quickly invert onto serving dish. Pour any remaining caramel around the custard; serve.