Preheat oven to 350°F fahrenheit with a pan of water for a water bath. Spray bunt cake pan with spray butter and set aside.

Put 4 eggs to blend in blender. Blend the eggs for 10 minutes. While eggs blend, begin to caramelize 1 cup of sugar over medium heat stirring often and keeping on eye on it so that it does not burn. While caramelizing sugar, prepare chocolate cake mix according to box instructions and set aside.

After the eggs have blended for 10 minutes add the condensed milk along with 1 can of water and the vanilla extract. Allow to blend until ready to use.

Once sugar has caramelized, pour into tube cake pan. Allow to cool just a few minutes before pouring in chocolate cake batter. Pour flan mixture over cake batter slowly and carefully around the pan. The flan mixture will mix with the cake batter but will separate during baking.

Place bunt cake pan in preheated oven in the pan of preheated water. Bake for 1 to 1 1/2 hours until toothpick inserted into cake batter comes out clean. Remove cake pan from water bath and allow to cool at least 1 hour. Carefully cut along outline of pan to separate cake and flan from bunt pan, invert onto serving dish. Store in refrigerator.