Mix the condensed milk with eggs, vanilla, milk and yeast mixture, flour and softened butter.
Divide the dough in half.
Mix one half of the dough with the two chocolates melted in the milk.
Pour both the plain mixture and the dark and milk chocolate mixture into a buttered and floured tin to create a marbled effect.
Bake the cake in a preheated oven at 180°C for 50 mins.
