Preheat oven to 180ºC . Butter 20 cm x 20 cm x 5 cm baking dish. Combine flour, sugar, 3 tablespoon cocoa powder, baking powder and salt. Stir in milk, butter and vanilla just until blended. Spoon into dish and spread evenly. In another bowl combine brown sugar, remaining 2 tablespoon cocoa; gradually stir in boiling water until sugar dissolves. Gently pour over batter in pan. Bake 25-30 mins until top of cake springs back when touched. Cool 30 mins and dust with confectioners sugar. Serve warm!
From The Chocolate Cookbook by Elizabeth Wolf Cohen