Boil condensed milk in the closed can for 2 hours in boiling water. Mix fat and 250 g sugar until creamy. Stir in eggs bit by bit. Mix flour with baking powder, stir in. Halve the dough.
Stir condensed milk, except 2 tablespoons, into one half of the dough. Chop the chocolate coating and melt over a warm water bath. Stir cocoa and chocolate coating into the second half of the dough. Fill the dough alternately by the spoonful into a greased springform pan (26 cm Ø). Use a fork to pull spirally through the dough. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 60 minutes. Leave to rest briefly in the pan, remove from the tin and allow to cool on a cake rack. Whip cream and 2 tablespoons of condensed milk until creamy, adding 2 tablespoons of sugar. Spread the cream on the cake.
Use a fork to pull spirally through the dough. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 60 minutes. Leave to rest briefly in the pan, remove from the tin and allow to cool on a cake rack. Whip cream and 2 tablespoons of condensed milk until creamy, adding 2 tablespoons of sugar. Spread the cream on the cake. Decorate with cocoa