In a large bowl, whisk together sugar, flour, cocoa, baking powder, baking soda and salt.
Then add eggs, milk, oil and vanilla to the flour mixture. Beat with a mixer on medium speed for 2 minutes.
Add the boiling water and stir until well combined (batter will be thin so do not be alarmed).
Pour batter into prepared pans and bake at 350 for 30 to 35 minutes or until wooden pick inserted in center comes out clean.
Cool 10 minutes and remove from pans to wire racks. Cool completely.
To prepare the frosting, place melted butter along with cocoa powder in a bowl and combine.
Then alternately add powdered sugar and milk, beating to spreading consistency.
Add small amount additional milk, if needed. Stir in vanilla.
Place one round cake on serving dish and top with a thin layer of frosting. Top with remaining cake round and frost entire cake with remaining frosting.