1. Make the (Egg-Free) Cookie Dough:

• Using a hand or stand mixer with the paddle attachment, cream together the 1/2 cup room temperature butter, 1/2 cup granulated sugar, and 2/3 cup light brown sugar until combined.
• Add the 1/4 cup milk and 2 tsp vanilla extract; mix until combined.
• Mix in the 2 cups heat-treated, cooled flour and 1/2 tsp salt on low speed until just combined.
• Fold in 1 cup of mini chocolate chips.
• Scoop (15) 1 1/2-tablespoon sized balls of dough using a small cookie scoop. Flatten them slightly into “patties.”
• Place the cookie dough patties on a plate lined with wax paper. Place this plate and the bowl containing any leftover dough in the refrigerator to chill.

2. Prepare for Cake Baking:

• Preheat the oven to 350°F (175°C).
• Grease three 8-inch round cake pans. Line the bottoms with parchment paper circles.
• In a small bowl, whisk together the 3 cups all-purpose flour, 2 tsp baking powder, and 1 tsp salt. Set aside.
• In a measuring glass or small bowl, combine the 1 cup whole milk and 2 tsp vanilla extract. Set aside.

3. Make the Cake Batter:

• In a large bowl using a hand or stand mixer (start with whisk attachment for creaming, switch to paddle later if desired), cream together the 1 1/2 cups room temperature butter and 2 cups granulated sugar on medium-high speed until very light and fluffy (about 3-5 minutes). Don’t skip this creaming time!
• Turn the speed down to medium. Add the 3 room temperature eggs one at a time, ensuring each egg is fully incorporated before adding the next.
• Mix in the room temperature Greek yogurt (or sour cream).
• With the mixer on low speed, alternate adding the flour mixture and the milk mixture, beginning and ending with the flour mixture (add flour in 3 parts, milk in 2 parts). Mix only until just combined after each addition.
• Gently fold in 1 cup of mini chocolate chips using a spatula.

4. Assemble and Bake Cakes:

• Divide the batter evenly between the three prepared cake pans. Spread it evenly.
• Remove the chilled cookie dough patties from the fridge. Gently push 5 patties down into the batter in each cake pan, distributing them evenly. Spread a bit of batter over the tops so they are covered.
• Bake for 30-35 minutes, or until a toothpick inserted into the cake portion (avoiding cookie dough) comes out clean. Rotate pans halfway through baking if needed.
• Let the cakes cool in the pans on wire racks for about 20 minutes.
• Carefully run a thin knife around the inside edge of the pans. Invert the cakes onto the cooling racks, peel off the parchment paper, and let them cool completely.
• Chill Layers: To prevent breakage during frosting, transfer the cooled layers to the fridge to chill for at least an hour before assembling. Wrap them in plastic wrap first.  

5. Make the Cookie Dough Buttercream:

• In a large bowl using a stand mixer with the paddle attachment (or hand mixer), cream together the 1 1/2 cups room temperature butter and 3/4 cup packed light brown sugar until smooth.
• Gradually mix in the sifted powdered sugar and the heat-treated, cooled flour, about 2 cups of the dry mix at a time, alternating with pouring in the 1/4 cup milk between additions. Mix on low until combined.
• Lastly, mix in the 1/2 tsp salt and 2 tsp vanilla extract until combined. Increase speed and beat until light and fluffy.
• Reserve Chips: Set aside the 1/2 cup mini chocolate chips; DO NOT mix them into the main batch of frosting yet.

6. Assemble the Cake Layers:

• If desired, level the tops of the chilled cake layers. Place the first cake layer on your serving plate.
• Spread an even layer of the cookie dough buttercream (without chips) between each cake layer (about 1 large heaping scoop per layer). Stack all three layers.
• Place the stacked, unfilled cake (“naked cake”) in the fridge for about 20 minutes to help the layers set.

7. Frost the Cake Exterior:

• Remove the cake from the fridge. Gently stir the reserved 1/2 cup mini chocolate chips into the remaining buttercream.
• Apply an even layer of this chocolate chip cookie dough buttercream over the entire outside (top and sides) of the cake. Smooth as desired.
• Place the cake back in the fridge while you prepare the ganache.

8. Make the Chocolate Ganache:

• Measure out the 4oz chopped bittersweet chocolate into a heatproof bowl and set aside.
• Pour the 1/2 cup heavy cream into a glass measuring cup. Heat in the microwave for about 1 minute, or until it just starts to bubble.
• Pour the hot cream over the chopped chocolate. Let sit for 5 minutes.
• Gently whisk until the ganache is completely smooth.
• Whisk in 2-3 teaspoons of vegetable oil to thin it out for dripping. Test the consistency: lift the whisk; if it flows back in a smooth, steady stream, it’s ready. If too thick, whisk in another teaspoon of oil. Let cool slightly if needed.

9. Apply Ganache and Final Decoration:

• Remove the chilled cake from the fridge.
• Immediately pour the slightly cooled ganache in the center of the cake top.
• Use a small offset spatula to gently push the ganache towards the edges, allowing it to drip down the sides naturally.
• Remove the leftover chilled cookie dough from the fridge. Crumble pieces of it all over the top of the cake, onto the setting ganache.

10. Serve:

• The cake is now ready to serve! It’s best enjoyed closer to room temperature. Slice and enjoy!