Preheat oven to 350°. In an (un-greased) 8x8 baking pan, mix flour, white sugar, ¼ cup of the cocoa, baking powder and salt (stir it up to combine) add the milk and oil and stir until the batter is well mixed.
Mix the brown sugar and ¼ cup of cocoa together and sprinkle evenly over the batter (do not mix it in).
Combine the boiling water, vanilla and instant coffee and gently pour it over everything (do not mix in it).
Bake for 35 minutes (the hot fudge sauce will bubble up from underneath and around the edges of the cake as it bakes).
Allow this to cool for 15 minutes before you serve it.
To serve, top a slice of cake with scoop of vanilla ice cream and spoon the hot fudge sauce over the ice cream.
