Preheat oven to 350°F. Lightly grease a 9x13 baking pan.
Prepare the cake mix as instructed on the box, DECREASING the eggs to ONE and swapping the water for milk (for a richer flavor). You will likely be combining the mix with approximately 1 cup milk, 1 egg, and ½ cup vegetable oil. Pour the batter into the prepared pan.
In a separate bowl, combine sugar, cocoa powder and espresso powder. Sprinkle the sugar mixture evenly over the top of the cake batter. If necessary, gently spread the sugar into a flat layer using the back of a spoon. Slowly and carefully pour the boiling water evenly over the top of the cake batter, do not stir.
Transfer to the oven and bake for 25-30 minutes, until the cake is cooked through and lightly springs back when you press it. Note: There will be a fudge sauce that has formed and is bubbling up under the cake, so make sure you are checking the cake only for doneness. Place pan on a wire rack to cool slightly. Enjoy warm, scooping the cake into a bowl and spooning sauce over the top.
You will also need milk, ONE egg and vegetable oil for preparing the cake mix. Prepare the mix as instructed on the box, DECREASING the eggs to ONE and swapping the water for milk. Using milk in place of water creates a richer cake. Reducing the eggs helps to keep this cake from being too moist and having any chance of an “eggy” flavor (since we are pouring boiling water over the raw batter).
I like to use a cake mix that has chocolate chips in it.