Preheat the oven to 350°F. Prepare three 6-inch or two 8-inch cake pans by spraying the sides with a cooking spray and a wax paper circle fitted to the bottom of the pan.

Sift the cake flour and then measure by spooning and leveling it in your measuring cup. Add the cake flour, baking powder, baking soda, salt, and espresso powder into a bowl and whisk to combine. Set aside. Combine the whole milk and coffee in a small container and set aside.

In the bowl of your stand mixer, cream the butter on high for two minutes until it's light and fluffy. Add in white and brown sugars and continue to mix on high for another two minutes, scraping down the bowl and paddle as needed. Add the eggs one at a time, mixing thoroughly after each addition. Add vanilla and sour cream and mix for one minute on high, scraping down the bowl and paddle once more.

With the mixer on low speed, add in the dry ingredients and mix until just combined. Add the coffee and whole milk mixture and mix until just incorporated. Scrape down the sides and bottom of the bowl and give it a few stirs to make sure there are no lumps. Batter will be slightly thick, but pourable.

Pour batter evenly into prepared cake pans (about ⅔ of the way full) and bake for 35-40 minutes. They're done when they spring back to the touch and a toothpick inserted into the middle comes out clean. Let the cakes cool in the pan for five minutes before turning them out onto a wire rack for an additional few hours of cooling. Make sure they're entirely room temperature before applying any frosting.

In the bowl of a stand mixer, cream the butter on med-high until light and fluffy (about 5 minutes), scraping down bowl and paddle a few times in between.

Add powdered sugar a few cups at a time, scraping down bowl and paddle between intervals. Mix on medium until fully incorporated.

Turn mixer to low and add vanilla and milk. Mix on medium for one minute. Scrape down bowl and paddle and add the instant espresso powder and salt. Mix for another minute on medium until incorporated.

Torte each layer to desired height. Fill the first layer with vanilla espresso buttercream and place the second layer on top. Fill the second layer with vanilla espresso buttercream before placing the final layer on top. Crumb coat with vanilla espresso buttercream and place in the refrigerator for 15 minutes to chill before frosting with a final layer of vanilla espresso buttercream.

Decorate however you wish.