For Sponge

1. Prepare two 6-inch round baking tins by greasing oil and placing butter paper on the bottom. Also, preheat the oven to 180° C or 350° F (OTG mode: lower rod + upper rod + fan).

For Sponge

1. In a saucepan, add Butter and let it melt slowly over medium-low heat.
2. As it melts, stir it continuously while swirling the pan frequently. Keep swirling until you have golden brown Butter and an intense nutty flavor. 
3. Take off the heat immediately and transfer it to a bowl so that the Butter stops cooking. Keep your eyes on the Butter, as it can be burnt very quickly.
4. Meanwhile, the brown Butter is cooling down; in a medium-sized bowl, sift the dry ingredients, which are all-purpose flour, baking powder, baking soda, and salt. Then, keep it aside.
5. Once the brown Butter has cooled down, add it to a big bowl along with brown sugar and cream it until it is light in color and fluffy in texture. It may take some time to cream them, so be patient and wait for the magic.
6. Once the creaming process is done, add in oil and beat again. Add in eggs, then beat again to incorporate properly.
7. Now, add all-purpose flour and buttermilk alternatively, starting with the flour mixture and finishing with it. 
8. Once incorporated properly, fold in the dark chocolate chips along with the vanilla essence. Mix properly to get a pourable batter without any lumps. Make sure to coat the chocolate chips with all-purpose flour before adding it to the batter.
9. Pour them into the prepared round baking tins equally. Use a kitchen weighing scale to get even layers. Bake them at 180° C or 350° F (OTG mode: lower rod mode only) for 30 to 35 minutes or until the toothpick inserted in the middle comes out clean.

For the Edible Cookie Dough

1. To heat treat all-purpose flour, spread the flour in the baking tray and bake it at 200° C or 400° F for 10 – 15 minutes, or until it turns light brown in color. Keep it aside to cool down. 
2. In a large bowl, cream butter along with castor sugar and brown sugar with an electric hand beater until it is light in texture and pale in color. 
3. Once creamed properly, add in heavy cream and vanilla essence, then beat again until they are mixed well.
4. Now, in the same bowl, sift in the heat-treated flour and give it a mix. Make sure that you sift the heat-treated flour as it forms lumps while heated. Lastly, add in the chopped chocolate and mix thoroughly. 

For Cookie Dough Buttercream

1. Make brown Butter with unsalted Butter (a) using the same method we did for the sponge batter and let it cool down completely. Keep it aside until we make the buttercream.
2. In a small bowl, mix heavy cream and brown sugar along with salt and vanilla essence. Warm it in a microwave until mixed properly. Warm it for only 15 – 20 seconds. The mixture will turn translucent. Let it cool down as well.
3. In a different medium size bowl, sift the icing sugar and heat-treated flour together. The heat-treated flour will give us the cookie dough flavor in the buttercream.
4. Now beat unsalted Butter (b) along with now cooled brown Butter until the mixture is fluffy in texture. 
5. Gradually add in the heavy cream and brown sugar mixture while beating it continuously.
6. Once mixed properly, add in icing sugar and heat-treated flour mixture in parts and keep beating until you have a nice and fluffy buttercream. Do not mix the chopped chocolate into the buttercream yet. 

For the Soaking Syrup

1. For the Soaking syrup, mix water and vanilla essence together, then keep it aside for the assembly.

For Dark Chocolate Drip

1.  In a microwave, melt the dark chocolate and war fresh cream separately. While melting dark chocolate, make sure that you melt it in a short burst of time, or it may burn. 
2. Now add the warm cream to the melted dark chocolate and mix to create a runny ganache-like texture. Transfer it to a piping bag and keep it aside.

Assembly

1. After the sponge has baked properly, let them cool down completely. De-mold the sponges from the baking tins with a bent palette knife while applying the pressure towards the tin and not the sponge. 
2. Now divide the sponges into two parts using a cake leveler. 
3. On a cake base, apply some of the frosting so that the cake does not budge while layering. Place one of the sponge layers on top and soak the soaking syrup using a pastry brush or with a spoon. 
4. Pipe buttercream on top and smooth out using the bent palette knife or offset spatula. 
5. Now spread the edible cookie dough on top of the buttercream, then place another layer of sponge, and repeat the same process as we did with the first layer until we get four-layered cakes.
6. For crumb coating the cake, pipe the buttercream all over the cake and smooth it out, then scrap the excess with a scrapper. It is okay if we can see the sponge through the frosting; we can cover it while doing the final frosting. 
7. Once crumb-coated, keep it in the refrigerator for 15 – 20 minutes to set the frosting.
8. For the final frosting, add the finely chopped chocolate to the remaining buttercream and mix properly. 
9. After 15 – 20 minutes, take out the cake from the refrigerator, pipe thick layers of buttercream all over the cake, and smooth it out. Make sure that you have sharp edges on top. 
10. Now add the drip around the top edge of the cake first, then fill in the center with it. Lastly, place edible cookie dough pieces around the top edge of the cake. And you are done with the most delicious cookie dough cake.