Steps to Make It
Gather the ingredients.
In a medium pot, place the milk and cream with the cinnamon stick. Bring almost to a simmer, then remove the pan from the heat and let it cool.
Preheat the oven to 325 F. Place the sugar in a small saucepan. Heat over medium heat, stirring occasionally, until sugar melts and turns a medium caramel brown.
Carefully pour the caramel into a 10-inch cake pan with tall sides, or into a 12-cup ring mold. Swirl the caramel evenly around the bottom of the pan, holding the edges of the pan with a towel (the pan may become very hot, even on the edges). The caramel will harden as it cools and may crack, which is fine.
Place the caramel-coated cake pan inside of a larger roasting pan with sides that are at least 2 inches high. Place a teapot full of water on the stove to boil.
Place the dulce de leche in a microwave-proof bowl. Heat it in the microwave briefly until the dulce de leche is very soft and spreadable.
In a large bowl, whisk the eggs.
Add the dulce de leche and condensed milk, and whisk until well mixed.
Remove the cinnamon stick from the milk and cream mixture, and whisk it into the egg mixture. Stir in the vanilla, and add a pinch of salt to taste.
Carefully pour the egg mixture through a sieve into the caramel coated cake pan.
Place the roasting pan, with cake pan inside, into the oven. Slide the oven rack out slightly, then fill the roasting pan with the boiling water until it reaches halfway up the side of the cake pan. Slide the oven rack back in place, and close the oven door.
Bake the flan for 1 hour to 1 hour and 20 minutes, or until it has an internal temperature of around 180 F (use a thermometer to take the temperature in the middle). The flan will still seem jiggly in the middle, but it will firm up as it cools.
Remove the flan from the oven, then let the flan cool in the water bath for about 10 minutes. Remove it from the water bath, and let it cool another 10 minutes. Loosen the edges of the flan with a knife, then flip the flan out onto a serving platter.
Serve flan warm, cold, or at room temperature.