Beat the eggs together with the sugar for the caramel mixture and then add the vanilla and milk.
For the cake: Beat the eggs with the sugar, milk, oil, baking powder, flour and cocoa.
Caramelize 5 tbsp sugar in a cake form and pour the caramel mixture in it.
Pour the cake mixture in the middle of the form. Place the form in another, larger form with 3/4″ (2 cm) of hot water in it. Let it cool in the water bath and then put it in the fridge with both forms overnight.
Invert the ready caramel cake in a platter the next day.