Layers of moist, flavorful coffee cake with decadent vanilla espresso buttercream
Preheat the oven to 350°F. Prepare three 8-inch or four 6-inch cake pans by spraying the sides with a cooking spray (Baker's Joy is my favorite) and a wax paper circle fitted to the bottom of the pan. Alternatively, you can grease and lightly flour the pans.
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 (a handheld mixer works fine too!), cream the butter for 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 2/3 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.
*DIY Cake Flour Recipe: To make your own cake flour, spoon and level one cup of all-purpose flour and remove 2 Tbsp. Add 2 Tbsp of cornstarch. Repeat per the amount of cake flour you need, then sift the flour and cornstarch mixture 4 times (don't skip that step!). After sifting, spoon and level to re-measure the amount of cake flour you need.
Make ahead tip: These cakes can be baked, cooled, wrapped in plastic wrap, and left out at room temperature up to two days ahead of decorating. Unfrosted cake layers can be wrapped tightly in plastic wrap and stored in the freezer for up to two months before thawing and frosting.
The buttercream can be made ahead and stored in an airtight container in the refrigerator for up to two weeks. When you're ready to use it, bring it back to room temperature and re-whip with your stand mixer.