1.Make the caramel by melting 1 cup sugar in a pan, over low heat. Keep your eye on it. If it burns you will have to start over. It is easier to clean if you use a non stick pan. Immediately pour the caramel into a 8-inch mold and quickly swirl it around to cover the bottom and a little up the sides. You have to be quick because the caramel hardens once it starts to cool down. The caramel should have cooled down before you pour the egg mixture in it, place in the roasting pan and set aside.
2.Preheat oven to 325 degrees F, bring a kettle of water to a boil for the water bath. Blend the whole milk, condensed milk, vanilla, and eggs in a blender until completely mixed. Pour the flan mixture through a metal strainer right into the caramelized mold.
3.Place the mold into a large cake pan or roasting pan. Pour enough hot water into the pan to come halfway up the sides of the mold. Carefully transfer to the middle oven rack. Bake for 30 to 45 minutes. Test the flan to see if it’s done by inserting a knife near the center. If the flan is still soft, let it cook longer until a knife inserted again comes out clean.
4.Remove from the oven carefully and let it cool on the counter to room temperature. Then cover with foil and refrigerate for at least 6 hours, preferably overnight. To serve run a knife around the inside of the mold to loosen the flan and lay a plate on top of the mold then carefully flip it over and slide the mold off.