To make the topping:
In a 2-quart saucepan, heat sugar, corn syrup and 1/3 cup water together over medium heat. Bring to a simmer and cook, without stirring, but swirl gently to evenly brown. Cook for about 10 minutes, or until the syrup turns deep golden in color. Remove pan from heat and pour syrup immediately into an 8-inch round cake pan. Swirl to coat bottom of the pan evenly. Allow syrup to cool and harden.
To make the custard:
In a medium saucepan, heat the milk and cream together over medium heat until steam appears and an instant-read thermometer reads 160 degrees when placed in the milk. Remove from heat.
Preheat the oven to 350 F.
In a kettle, bring 2 quarts of water to a boil.
Place the eggs, sugar, vanilla and salt in a blender. Blend on medium speed for 1 minute. With the blender running on low, remove the cap from the blender top and slowly pour the milk mixture into the blender. Blend for 1 minute. Pour the egg and milk mixture into the cake pan over the hardened syrup.
Place the cake pan in a larger baking pan. Pour boiling water into the baking pan to reach halfway up the sides of the round pan, forming a water bath. Cover the baking pan loosely with foil. Bake for 65 to 70 minutes, until the custard is set. Remove the inner pan to a wire rack and let it cool to room temperature.
To unmold the flan, run a butter knife around the inside edge of the pan to loosen the custard. Place an inverted large plate over the top. Quickly turn over the plate and pan together. Gently shake the pan to release the custard. Serve immediately.
CHEFS Note: This recipe can be made in individual servings. Working quickly, pour portions into 8 small ramekins and reduce baking time to 35 to 40 minutes.