- To make the cake: Preheat the oven to 350°F. Prepare two 9-inch cake pans by greasing with nonstick spray or butter, then lightly flouring.
- In a large mixing bowl, combine the flour, granulated sugar, cocoa powder, baking powder, baking soda, espresso powder, cinnamon, and salt and whisk to combine.
- Add the milk, oil, eggs, and vanilla to the flour mixture and mix together with an electric mixer on medium speed until well combined. Reduce the speed and carefully add the boiling water to the batter; mix until well combined.
- Divide the cake batter evenly between the prepared cake pans. Bake until a toothpick or cake tester inserted in the center of the cake comes out clean, 30-35 minutes.
- Remove from the oven and let cool for about 10 minutes. Remove the cakes from the pans and let cool completely on a wire rack.
- Meanwhile, to make the frosting: Place the cocoa powder in a large mixing bowl and whisk well to remove any lumps. Add the butter and beat until smooth and very well combined. Add 1 cup confectioners' sugar followed by about 1 tablespoon milk and mix until well combined, then
- increase the mixer speed to high and beat for about 1 minute. Repeat until the confectioners' sugar and milk have been added, then add the vanilla extract and mix well.
- Frost the cake with the frosting.
Note: Cake can be made and frosted up to 1 day ahead and kept at cool room temperature