Preheat oven to 350 º F (180 ºC), and grease mold.
Pour dulce de leche in the bottom of your baking pan. Place your mold in larger pan. Add enough boiling water to larger pan to come halfway up side of your baking pan.
Prepare the brownie batter. Put the chocolate and butter in a medium heatproof bowl and set over a pan of simmering water, or melt in the microwave. Melt the chocolate and butter, stirring occasionally until smooth. Remove from heat and set aside to cool.
In another medium bowl whisk together the eggs and sugar at low-medium speed until combined. Whisk the warm chocolate mixture into the egg mixture. Stir in the flour, salt and cocoa powder with a wooden spoon until just combined. Pour brownie mixture into the mold.
Prepare the flan mixture. Place the eggs, vanilla, milk and sweetened condensed milk in a blender and puree until smooth. Pour the flan mixture on top of the brownie mixture.
Cover pan with foil sprayed with cooking spray, sprayed-side down.
Place in the oven and bake for about 45 to 60 minutes, depending on your mold. Last 15 minutes, cook uncovered.
Remove from the oven, and once cool, refrigerate at least 12 hours before unmolding and eating.
