Beat the eggs with the sugar, yoghurt and oil. Add the rest of the ingredients and beat until homogeneous.
Set aside 1 cup of the mixture and stir the cocoa in it well.
Pour the mixture without the cocoa into a buttered and floured cake form. Pour the cocoa mixture over it, making swirls carefully on top.
Bake in a preheated 392°F (200 °C) oven for 35-40 min. or until ready. Leave the cake to cool well.
Crumble the chocolate into small pieces, put them in a water bath to melt with the milk, stir until you get a homogeneous mixture.
Pour the warm glaze over the cooled cake and sprinkle with chocolate sprinkles on top. Leave the glaze to set.