Add sugar to milk and heat it, completely dissolve sugar.
In a separate bowl, combine cocoa, flour and baking powder.
Pour milk into the dry ingredients and mix until smooth so that there are no lumps.
Add grated chocolate and orange zest to the dough.
Pour in the orange juice and mix again. The dough should be something like a pancake.
Pour the dough into a mold and bake in a preheated oven to 180 degrees 45 minutes.
Let the finished cake cool completely, and only then remove it. Sprinkle with powdered sugar and can be served.