Preheat oven to 350º F. Prepare one 9x13 baking dish by spraying with baking spray or buttering and lightly flouring.
For the cake:
Whisk together add flour, sugar, cocoa, baking powder, baking soda, salt and espresso powder to a large mixing bowl.
Add milk, vegetable oil, eggs, and vanilla to flour mixture and mix together until well combined. Carefully stir the boiling water into the cake batter and pour into the prepared 9x13 dish.
Bake for 30-35 minutes, until a toothpick or cake tester inserted in the center comes out clean.
Remove from the oven and allow to cool completely.
Chocolate Buttercream Frosting (9x13 Recipe)
Add cocoa to a large bowl or bowl of stand mixer. Whisk through to remove any lumps.
Add the butter and cream together butter and cocoa powder until well-combined.
Add sugar and milk to cocoa mixture by adding 1 cup of sugar followed by about a tablespoon of milk. After each addition has been combined, turn mixer onto a high speed for about a minute. Repeat until all sugar and milk have been added.
Add vanilla extract and espresso powder and combine well.
If frosting appears too dry, add more milk, a tablespoon at a time until it reaches the right consistency. If it appears to wet and does not hold its form, add more confectioner’s sugar, a tablespoon at a time until it reaches the right consistency.
Spread the frosting on top of the cooled cake. Cover and keep on the counter for up to 3 days for best taste.