Preheat the oven to 350°. Spray a 9-inch square baking pan with nonstick spray.
Combine the flour, granulated sugar, the 1/3 cup of cocoa powder, the baking powder, espresso powder, baking soda, and salt in a large bowl. Make a well in the center, and pour in the milk, melted butter, and vanilla. Stir just until blended; spoon the batter evenly into the pan.
Combine the brown sugar and additional 1/4 cup 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.
Tip: Serve this fudgy favorite with a scoop of vanilla or coffee fat-free frozen yogurt; 1/2 cup with each serving will increase the points by 2.