Preheat oven to 325º F. Grease 2 cookie sheets or half sheet pans with at least a 1" lip (17 1/4" x 12 1/4" x 1")
Add flour, sugar, cocoa, baking powder, baking soda, and salt to a large bowl of a stand mixer. Using paddle attachment, stir through flour mixture until combined well.
Add milk, vegetable oil and eggs to flour mixture and mix together on medium speed until well combined. In a microwave safe glass, heat water until boiled. Remove from microwave and add espresso powder and mix well. With mixer on low speed, carefully add boiling espresso water to the cake batter. Increase to high speed for about 1 minute to add air to the batter, scraping the bottom to ensure it's fully incorporated.
Evenly distribute cake batter onto prepared sheet pans, coming about half way up the pans. Bake in the oven until a toothpick inserted in the center comes out clean, about 20 minutes. Remove from the oven and allow the cakes to cool completely. Turn onto cooling racks to completely cool before frosting.