In a large bowl cream together the butter and the sugar. Add the eggs, salt, rum flavouring and almonds and combine well.
Now slowly start to stir in the flour. In the end add the cocoa. It might take a while until it's all incorporated and the dough is quite tough in the end. Don't be tempted to add any liquid to it! It's suppoed to be that way.
Line a baking sheet with baking paper and spread the dough around 1cm thick onto it with a spatula. You need a bit of patience for that step, because the dough is very sticky. To make it easier you can brush some cold milk onto the dough.
Bake for 35 minutes.
When the berlin bread comes out of the oven, quickly prepare the glaze. With the confectioners' sugar and the warm water make a water icing. Don't make it too thick! It should not be very viscous.
Spread the glaze onto the dough immidiately and cut into squares with a pizza cutter while it's still hot.
I'd highly recommend a stand mixer or a food processor for making the dough. You can use a hand mixer, but since the dough gets so tough it's quite a bit of work.