A decadent chocolate chip cookie flavored cake topped with vanilla buttercream and extra chocolate chip cookies for good measure.
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, and salt into a bowl and whisk to combine. 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 medium-high for another two minutes, scraping down the bowl and paddle as needed. Turn the mixer to low and add the eggs one at a time. Add the vanilla and sour cream, turn the mixer to high, and mix for one minute, 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 whole milk 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, then fold in the flour-coated chocolate chips. 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. The cakes are 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.
With a hand mixer or paddle attachment on your stand mixer, cream the butter on medium-high until it’s creamy and light (almost white) in color. About 7 minutes.
Add the powdered sugar, one cup at a time, scraping down after each addition and making sure each cup is fully incorporated before adding the next one. Add vanilla, milk, and salt and mix on medium-low for another two minutes until fully incorporated.
Fill and frost the cake layers with vanilla buttercream. Crumble the chocolate chip cookies (either homemade or store-bought) and garnish the cake by adding them to the bottom third of the frosted cake, pressing the crumbles in to the sides.
Make Ahead Tips: the cake layers can be made ahead and stored (wrapped in plastic) at room temperature for up to one day. Alternatively, you can wrap the cake layers in plastic and store them in the freezer for up to two months. When you're ready to use them, thaw them to room temperature before continuing with the frosting and decorating process.
The vanilla buttercream can be made ahead and stored in an airtight container at room temperature for up to one day. Alternatively, you can store it 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 on medium for one minute to bring it back to frosting consistency.