Spray a 9 inch pan with oil. Line the base of the cake with parchment paper. Flour the sides of the cake pan with cocoa powder.
Preheat oven to 350 F.
In a large bowl, sift the flour, cocoa, sugar, baking soda, baking powder and salt.
In another bowl, whisk together milk, oil, egg and vanilla.
Make a well in the centre of the flour mixture and pour the wet ingredients. Fold in gently till just incorporated. Pour over the hot coffee and gently(dont not whisk) everything so that you can see a smooth shiny brown batter with no streaks of white flour. The batter will be quite runny but its all okay.
Pour into the prepared pan and bake for 28-32 minutes or un till a skewer inserted in the centre of the cake comes out clean. The cake will start to pull away from the sides slightly.
Take out of the oven and let cool for 10 minutes in the pan. Run a knife all around and take out the cake out of the pan on to a cooling rack. Cool completely. Once cooled, you can store the cake in the fridge for 2-3 days. This cake freezes easily, just wrap the cake in a cling film followed by placing it in a large ziploc and freeze upto a month.
If you are making trifle cake next morning, poke holes all over in the cake and pour Kirsch all over, let soak up. Store the cake overnight or for 2-3 hours atleast. For the trifle, cut up the cake into small cubes using a sharp knife or cut rounds the size of the serving bowl as you wish.