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

• Using a hand or stand mixer with the paddle attachment, cream together the room temperature butter, granulated sugar, and light brown sugar until combined.
• Add the milk and vanilla extract; mix until combined.
• Mix in the heat-treated, cooled flour and 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 any leftover bowl of dough in the refrigerator to chill while you make the cake batter.

2. Prepare for Cake Baking:

• Preheat the oven to 350°F (175°C).
• Grease three 8-inch round cake pans well. Line the bottoms with parchment paper circles and grease the parchment.
• In a small bowl, whisk together the 3 cups of all-purpose flour, baking powder, and 1 tsp salt. Set aside.
• In a measuring glass or small bowl, combine the whole milk and 2 tsp vanilla extract. Set aside. (Note: Original recipe mixed vanilla with milk, corrected here based on standard creaming method steps described).

3. Make the Cake Batter:

• In a large bowl using a hand or stand mixer (preferably with whisk attachment for creaming, then switch to paddle), 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). Scrape down the bowl.
• Turn the speed down to medium. Add the room temperature eggs one at a time, beating well until fully incorporated after each addition.
• Mix in the room temperature Greek yogurt (or sour cream) and 2 tsp vanilla extract. (Added vanilla here as typical).
• With the mixer on low speed, alternate adding the flour mixture and the milk mixture, beginning and ending with the flour mixture (Flour-Milk-Flour-Milk-Flour). Mix only until just combined after each addition. Do not overmix.
• Gently fold in 1 cup of mini chocolate chips.

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. You can gently 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 or with a few moist crumbs. Rotate pans halfway through if needed for even baking.
• 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 (at least 1-2 hours).
• Optional but Recommended: Once cool, wrap the layers in plastic wrap and chill in the fridge for at least an hour (or freeze briefly) before assembling. This makes frosting much easier.

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 at a time, alternating with the 1/4 cup milk. Start and end with the dry ingredients. Mix on low speed until just combined.
• Add the 1/2 tsp salt and 2 tsp vanilla extract. Increase speed to medium-high and beat until light and fluffy, 2-3 minutes.
• Set aside the 1/2 cup mini chocolate chips for now. 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 with a serrated knife.
• Place one cake layer on your serving plate. Spread a generous, even layer of the cookie dough buttercream over the top (about 1 large scoop, as recipe suggests).
• Place the second cake layer on top, pressing gently. Spread another layer of buttercream.
• Place the third cake layer on top (upside down for a flat top surface).
• Apply a thin “crumb coat” of the buttercream over the entire cake. Chill the “naked” cake in the fridge for about 20 minutes to set the crumb coat.  

7. Frost the Cake Exterior:

• 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 top and sides of the chilled cake. Smooth with an offset spatula or bench scraper.
• Place the cake back in the fridge while you prepare the ganache.

8. Make the Chocolate Ganache:

• Place the chopped bittersweet chocolate in a small heatproof bowl.
• Heat the heavy cream in a small saucepan or microwave until hot and just beginning to bubble (about 1 minute in microwave).
• Pour the hot cream over the chopped chocolate. Let sit for 5 minutes without stirring.
• Gently whisk until the ganache is smooth and glossy.
• Whisk in 2-3 teaspoons of vegetable oil until combined. Check the consistency for dripping: lift the whisk; if it runs back into the bowl in a smooth, steady stream, it’s ready. If too thick, add another teaspoon of oil. Let cool slightly if it seems too thin or hot.

9. Apply Ganache Drip and Serve:

• Remove the chilled cake from the fridge.
• Carefully spoon or pour the slightly cooled ganache around the top edge of the cake, allowing it to drip down the sides. Control the drips by adjusting the amount poured.
• Pour any remaining ganache you desire over the top center.
• Let the ganache set slightly (can chill briefly if needed). Slice and serve. It’s best served closer to room temperature.