Whisk together the flour, cocoa powder, salt, and white sugar for the first layer. Mix in the milk, vanilla, and melted butter. Spread evenly into the bottom of a small (8x8 or slightly smaller) baking dish.
In a separate bowl, whisk together the brown sugar and ¼ cup cocoa powder. Sprinkle evenly over the first layer.
Pour the boiling water into the dish (I deflect it with a spoon so it doesn't make huge holes) and bake for 45 minutes.
Serve warm with vanilla ice cream.
Recipe by The Kitchen Paper at http://c02.ddd.mwp.accessdomain.com/hot-fudge-pudding-cake/