Preheat oven to 180C (350F). Grease a 20cm round cake tin and line with baking paper
In a bowl, sift flour, salt, baking powder and cocoa together
Add milk, butter, sugar and eggs and mix until pale and fluffy
When the mixture is evenly combined, spread into the prepared cake tin, and bake for 45 minutes, or until a toothpick comes out clean when inserted into the cake.
Allow cake to cool
To make frosting, beat the melted butter in a mixer for 30 seconds. Add milk and vanilla extract, then mix to combine.
Add icing sugar and cocoa powder and stir until incorporated.
Spread over the top of the cooled cake, and serve