Preheat oven to 350°F. Spray 10-cup Bundt pan with no stick cooking spray. Spread 1/2 cup of the dulce de leche in bottom of prepared pan. Place Bundt pan in large roasting pan. Set aside.
Beat eggs, sweetened condensed milk, evaporated milk, cream cheese, and 1 teaspoon of the vanilla in large bowl with electric mixer on medium speed (or with wire whisk) until well blended. Set aside.
Prepare cake mix as directed on package, adding remaining 2 teaspoons vanilla. Pour batter over dulce de leche in pan. Slowly pour flan mixture over batter. Cover pan with foil sprayed with no stick cooking spray. Carefully pour hot water into roasting pan to come halfway up sides of Bundt pan.
Bake 1 hour or until toothpick inserted near center comes out clean. Transfer Bundt pan from water bath to wire rack. Remove foil. Cool completely.
Refrigerate at least 6 hours or overnight. Loosen cake from sides of pan. To unmold, invert pan onto a serving platter. Remove pan. Mix remaining dulce de leche and milk in small saucepan. Cook and stir over medium heat until mixture reaches pourable consistency. Pour or spoon over Chocoflan to serve.