Jake's Oreo Cake with Chocolate Pan Frosting

My son's thirteenth birthday was back in January but I completely forgot to post about his cake! Jake went totally bonkers over it and said it was the best birthday cake I have ever made for him. Sometimes it's the simple recipes that make the biggest impression.
It's a fairly easy cake to make, both kid and adult friendly, and, because it's cake mix based, it's doesn't take very long to prepare. To save a little money and to keep from having a big package of Oreos in the house (big temptation for me), I used one 8oz package of Mini Oreos instead of 18 full size cookies. The little cookies also came in handy for decorating the cake too. The frosting was almost too good to be true; super creamy, chocolaty but not too much, and complimented the flavor of the Oreos perfectly.

Oreo Cake with Chocolate Pan Frosting
Yield: 8 slices (or more depending on how you slice it)
adapted from Cake Mix Doctor

Cake
18 full-sized Oreos or one 8oz package of mini Oreos or 2 1/4 cups of chocolate cookie crumbs
1 package (18oz) of white cake mix WITH pudding in the mix
1 cup water (room temperature)
1/2 cup vegetable oil
3 large eggs, at room temperature

Frosting
2/3 cup unsweetened cocoa powder
6 tablespoons boiling water (plus additional, if needed)
1 stick of unsalted butter, at room temperature
3 cups powdered sugar, sifted (plus additional, if needed)
1 teaspoon pure vanilla extract
pinch of kosher salt

Cake
Preheat the oven to 350F. Spray two 9" cake pans with Pam for baking or grease with shortening and dust evenly with flour, tapping out the excess. Set the pans aside.

Grind the cookies in a food processor and process them until you have a fine crumb. If you don't have a food processor, you can put the cookies in a zip-lock style bag, squeeze all the air out, and crush them using the bottom of pot or a rolling pin. You'll need 2 1/4 cups of crumbs total. If you have more than this, set them aside to use to decorate the cake (if desired). Set aside.

Place the cake mix, water, eggs, and oil in a large mixing bowl and mix on low speed for 1 minute and scrape the bowl and blade. Increase the speed to medium and mix for another 2 minutes and scrape the bowl and blade. The batter should look evenly colored. Add the cookie crumbs and mix on low for 15 seconds or so until all the crumbs look evenly distributed.

Pour the batter evenly between the two pans and smooth the tops. Bake both pans in the oven, side by side, and bake about 25-30 minutes until a cake tester in the center of the cake comes out clean. Remove the cakes from the oven and cool on wire racks for 10 minutes. Run a knife around the edge of the pans and invert onto the rack. Then invert each cake again so they continue to cool right-side-up. Allow to cook completely 30 minutes more.

Frosting
Place the cocoa powder in the mixing bowl of your stand mixer and pour the boiling water over it. Stir the cocoa and water with wooden spoon or rubber spatula until it comes together to create a soft mass. Add the butter and blend on low with the paddle attachment on low speed until the mixture is smooth and well combined, about 30 seconds. Add the vanilla and salt and mix for 30 more seconds. Scrape the bowl and blade.

Add 1 cup of powdered sugar and beat on low speed until all the sugar is incorporated. Repeat with the other 2 cups. Scape bowl and blade. Increase the speed to medium and beat until the frosting has lightened in color and is fluffy, about 2 minutes more. Add more boiling water, a teaspoon at a time, or more powdered sugar, a tablespoon at a time, if the frosting is too thick or too thin.

Assembly
Slice each cake horizontally (if desired) so you have 4 layers of cake (I like to do this using a long piece of unflavored dental floss). Place a little bit of frosting on the bottom of your cake plate (this will act like glue and hold the cake in place). Place one of the cake slices cut side up on the plate. Top with some frosting and smooth to about 1/2 from the edge. Repeat the process with the remaining 3 layers. Then frost the top and side of the cake. Decorate the cake with reserved cookies, cookie crumbs, and cake crumbs or any way you wish.

Cut and serve right away or let it sit at room temperature until you're ready to eat.