For the caramel: Place the sugar in a saucepan and heat until it melts and turns golden brown. Pour the caramel into a baking pan.

For the cake: In a bowl, combine the egg, vanilla extract, milk, sugar, and oil. Mix well until fully combined.

Add the flour and cocoa powder. Mix until smooth and no lumps remain.

For the flan: In a bowl, combine the milk, sugar, and vanilla extract. Mix well until the sugar dissolves. Add the eggs and mix until fully incorporated.

Pour the flan mixture into the pan and let it sit for a moment to allow the foam to settle. Place the pan in a larger baking dish filled with water.

Bake in a water bath at 320°F (160°C) for about 1 hour.

Check for doneness by inserting a toothpick; it should come out clean.