1. Preheat oven to 350. Spray a 9-inch-square baking pan with nonstick spray.
2. Combine the flour, granulated sugar the 1/3 cup of cocoa powder, the baking powder, espresso powder, baking soda, and salt in a large bow. Make a well in the center, and pour in the milk melted butter, and vanilla. Stir just until blended; spoon th batter evenly into the pan.
3. Combine the brown sugar and the additional 1/4 up cocoa powder in a small bowl. Sprinkle evenly over the batter. Gently pour the boiling water in a zigzag fashion over the top; do not stir. Bake until the top of the pudding is set, about 35 minutes. Cool on a rack at least 30 minutes. Cut into 9 squares and serve warm or at room temperature.