Let’s bake this incredible Cookie Dough Cake! First, prepare the edible cookie dough component, remembering the crucial flour safety step. Heat-treat 3 cups of all-purpose flour (2 cups for dough, 1 cup for frosting) as described above (bake at 350°F for 5-7 mins, cool completely).

Make the Cookie Dough: Using a hand or stand mixer with the paddle attachment, cream together the room temperature butter, granulated sugar, and packed light brown sugar until well combined and fluffy. Add the milk and vanilla extract and mix until combined. On low speed, mix in the 2 cups of cooled heat-treated flour and the salt until just combined. Fold in the 1 cup of mini chocolate chips.

Scoop about 15 portions of cookie dough using a small cookie scoop (approx. 1 1/2 tbsp size). Flatten each scoop slightly into a small patty or disc. Place these patties on a plate lined with wax paper. Wrap the remaining cookie dough well and place both the patties and the leftover dough block in the refrigerator to chill while you make the cake batter.

Make the Cookie Dough Cake layers: Preheat the oven to 350°F (175°C). Prepare three 8-inch round cake pans with non-stick spray and parchment paper rounds on the bottom. In a small bowl, whisk together the 3 cups all-purpose flour (this flour does NOT need heat-treating as it will be baked), baking powder, and salt. Set aside. In a liquid measuring cup, combine the room temperature whole milk and the 2 tsp vanilla extract. Set aside.

In a large bowl using a hand or stand mixer (clean bowl, whisk attachment recommended for creaming), cream together the room temperature butter and granulated sugar on medium-high speed until very light and fluffy, about 3-5 minutes. Scrape down the bowl. Reduce speed to medium and add the room temperature eggs one at a time, beating well after each until fully incorporated. Beat in the room temperature Greek yogurt or sour cream.

Alternate adding the dry ingredient mixture and the milk mixture to the creamed butter/egg mixture, beginning and ending with the dry ingredients. Add about one-third of the dry mix, beat on low until almost combined. Add about half of the milk mixture, beat on low until just combined. Repeat with another third of dry, the remaining half of milk, and finish with the last third of dry ingredients. Mix only until just combined after the last addition. Gently fold in the 1 cup of mini chocolate chips using a spatula.

Divide the cake batter evenly among the three prepared cake pans. Retrieve the chilled cookie dough patties from the fridge. Gently press 5 patties down into the batter in each cake pan, distributing them evenly. Use a spatula to gently spread a little batter back over the tops of the patties so they are mostly covered.

Bake for 30-35 minutes, or until a wooden toothpick inserted into the cake portion (avoiding cookie dough) in the center comes out clean or with a few moist crumbs. Rotate pans halfway through if needed for even baking. Let the cakes cool in their pans on wire racks for about 20 minutes. Then, carefully run a knife around the edges and invert the cakes onto the racks. Peel off the parchment paper and let them cool completely. Once cool, wrap the layers and chill them in the fridge for at least an hour before assembling (this helps firm them up for easier handling).

Make the Cookie Dough Buttercream: In a large bowl (stand mixer with paddle or handheld), cream the room temperature butter and the packed light brown sugar together until smooth and fluffy. On low speed, gradually mix in the sifted powdered sugar and the 1 cup of cooled heat-treated flour, alternating with additions of the 1/4 cup of milk (add milk between sugar/flour additions). Mix until everything is incorporated. Add the salt and vanilla extract. Increase speed to medium-high and beat for 2-3 minutes until light and fluffy. Set aside about 1/2 cup of mini chocolate chips; stir the rest into the main batch of frosting only when ready to do the final frosting coat, not before the crumb coat.

Assemble the cake: Level the tops of the chilled cake layers if desired. Place the first layer on your serving plate. Spread a generous, even layer of the cookie dough buttercream (without the final addition of chips yet) over the top (about 1 large scoop). Place the second layer on top and repeat with another layer of buttercream. Place the third layer on top, upside down for a flat top surface. Apply a thin crumb coat of the buttercream all over the cake. Chill the naked cake for about 20 minutes to set the layers and crumb coat.

Remove the cake from the fridge. Stir the reserved 1/2 cup of mini chocolate chips into the remaining buttercream. Apply an even layer of this finished cookie dough buttercream to the outside (top and sides) of the cake, smoothing as desired. Place the cake back in the fridge while you prepare the ganache.

Make the Chocolate Ganache: Place the chopped bittersweet chocolate in a heatproof bowl. Heat the heavy cream in a glass measuring cup in the microwave for about 1 minute, or until just bubbling (or heat in a saucepan). Pour the hot cream over the chopped chocolate. Let sit for 2-3 minutes, then whisk until completely smooth. Whisk in 2-3 teaspoons of vegetable oil until the ganache is smooth and has a nice dripping consistency (test by lifting whisk – should fall in a smooth stream). Let cool slightly until barely warm but still fluid.

Immediately pour the slightly cooled ganache onto the center of the chilled cake. Use a small offset spatula to gently push the ganache towards the edges, allowing it to drip down the sides naturally. Retrieve the block of leftover chilled edible cookie dough from the fridge. Crumble small pieces of this dough all over the top of the wet ganache. Your cake is ready! Serve relatively soon or refrigerate.