Preheat oven to 350°.
Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 2/3 cup sugar, 1/4 cup cocoa, coffee granules, baking powder, and salt in a bowl. Combine milk, oil, and vanilla in a bowl; add to flour mixture, and stir well. Spoon batter into an 8-inch square baking dish coated with cooking spray.
Combine 1/3 cup sugar and 2 tablespoons cocoa. Sprinkle over batter. Pour 1 cup boiling water over batter (do not stir). Bake at 350° for 30 minutes or until the cake springs back when touched lightly in the center (cake will not test clean when a wooden pick is inserted in center). Serve warm with ice cream.
Note: This recipe is easy to double. Spoon into a 13 x 9-inch baking dish; bake at the same temperature and time.