Beat egg whites with a pinch of salt until stiff peaks form. Gradually add 180g sugar. Set aside a few spoonfuls.

In a separate bowl, beat egg yolks with the remaining sugar until light.

Mix in water, flour, cocoa, and baking powder until smooth.

Carefully fold in the beaten egg whites.

Bake in a 20cm cake pan at 180°C for 40 minutes.

For the cream filling, cook eggs, sugar, starch, condensed milk, and milk until thickened. Add vanilla and cool.

Cut the cooled cake in half, soak with sweetened milk if desired.

Blend the cooled cream with butter and assemble the cake.

Refrigerate for 3-4 hours.

For the frosting, cook cocoa, sugar, and sour cream on low heat.

Decorate the cake and serve!