Preheat the oven to 350°F. Grease a 13X9 baking dish with butter, line the bottom and sides of the pan with parchment paper, and grease the paper. (I’ll let you just grease, line the bottom of the pan, and lightly flour the sides if you’re feeling lazy.)
Place a large sifter or a sieve in a large mixing bowl. Add the flour, cocoa, baking powder, baking soda, and salt and sift. Add the sugar and whisk until combined.
In another large bowl, whisk the eggs, milk, oil, and vanilla together.
Gradually add the wet ingredients to the dry ingredients and whisk until there are no lumps and the batter is smooth.
Carefully pour in the boiling water and espresso and stir until combined. (Watch the little ones with the hot water!) Pour the batter into the prepared pan.
Bake in the center of the oven for approximately 30 minutes or until a wooden skewer inserted in the center comes out clean, and the cake bounces back when lightly pressed.
Sift powdered sugar over the top and you're done!