Sieve together Flour,sugar,cocoa powder,baking soda,salt and keep aside.
In another bowl mix together wet ingredients and add in dry ingredients ,combine well until smooth batter.
pour into a greased pan and bake @180 c for 30 minutes,until tooth pick inserted comes out clean.
when the cake is baked remove onto the wire rack and allow it to cool..
To prepare buttercream frosting
Beat together butter,powdered sugar ,cocoa powder and vanilla essence ..Adjust the consistency with adding the milk until you get a spreadable buttercream.