Preheat oven to 160 degrees. Keep a 24 cm springfoam pan ready, by greasing it well and lining the bottom with parchment paper.
Combine the condensed milk, butter, water and vanilla till well whisked.
Sift the dry ingredients over it and fold in till the mixture is moist. Do not over-mix.
Pour into the prepared pan and smooth the top. Bake for 30 to 40 minutes till a skewer comes out clean.
Cool in the tin for 10 minutes, then slowly move the cake from the tin to a wire rack and cool completely.
To prepare the icing, mix the butter, cocoa powder and icing sugar and add water one tablespoon at a time till you get a thick consistency. I used 2 tbsp of water.
Spread over cooled cake and allow it to set. Slice and serve.