Melt the butter and add the milk. Whisk the eggs and the sugar until white and puffy. Then add the milk and butter. Mix the dry ingredients and add them to the batter. Stir until smooth.
Pour in a big oven tray covered with grease proof paper. Bake for 30 minutes in 175°C. Let cool.
Mix icing sugar and water until smooth and spread on top of the cake.