Sift cocoa powder, flour, baking powder, baking soda, sugar and salt into a large bowl.
In a seperate bowl whisk milk, vegetable oil, apple cider vinegar and vanilla together until combined.
Pour liquid ingredients into the flour mixture, stir until smooth.
Spoon mixture into cupcake cases, filling them half way.
Bake for approximately 10 minutes, or until a skewer inserted into the centre comes out clean. Cool completely on a wire wrack.
While cakes are cooling beat cream cheese and butter in a medium bowl with an electric mixer until smooth. Add milk and vanilla, then gradually add icing sugar until frosting is as thick or thin as you would like it.
Spread or pipe frosting onto cakes. Leave for a few minutes to set then serve.