Make the brownies

1. Line the bottoms of three 8 inch cake pans with parchment paper and grease the sides. Preheat oven to 350 degrees.
2. Add the oil, sugar and vanilla extract to a large bowl and whisk together until well combined. Add the eggs and mix until well combined.
3. Combine flour, cocoa, baking powder and salt in a medium sized bowl. Add the dry ingredients to the wet ingredients and mix together until well combined, but don’t over mix.
4. Divide the batter evenly between the three pans and spread evenly.
5. Bake for 25-30 minutes, or until a toothpick comes out with a few crumbs.
6. Remove brownies from oven and allow to cool for about 10 minutes in the pan, then remove to cool on wire rack.
7. While brownies cool, make cookie dough.

Make the cookie dough

1. Add the butter and sugars to a large mixer bowl and beat together until light and fluffy, about 3-4 minutes.
2. Add the peanut butter and vanilla extract and beat until well combined.
3. Add the flour and salt and mix just until well combined.
4. Add milk to achieve the preferred cookie dough thickness.
5. Stir in the chocolate chips. The cookie dough will be thick. Set aside.

Assemble the cake

1. Once the brownies are cool, it’s time to put the layers together. You can pile the cookie dough onto the brownies, stack the layers and leave messy layers, or use the method I used for having clean edges/sides of the cake.
2. Place half of chocolate chips in a medium sized bowl. Microwave half of the heavy cream until it starts to boil. Remove from microwave and pour over chocolate chips.
3. Cover bowl with saran wrap and let sit for 5-7 minutes, then whisk together until smooth.
4. Using one of the same 8 inch cake pans that you baked the brownies in, put parchment paper or saran wrap in the bottom and up the sides of the pan. You will use it to lift the layers out of the pan.
5. Place the first brownie into the bottom of the pan.
6. Add about 3 tbsp of chocolate ganache on top of the brownie and spread into a thin layer. This will help the cookie dough stick to the brownie.
7. Put half of the cookie into the pan and spread evenly on top of the brownie. Remove the first two layers from the cake pan and place it on a serving dish.
8. Repeat steps 5-7 with the second brownie and remaining cookie dough, then remove from pan.
9. Put another 3 tbsp of chocolate ganache on top of the cookie dough layer from the first section of cake and spread thinly. Place the second section of cake onto the first.
10. Put another 3 tbsp of chocolate ganache on top of the cookie dough layer on top (the fourth layer) and spread thinly. Top with remaining brownie.

Decorate the cake

1. Place remaining chocolate chips in a medium size bowl. Microwave remaining heavy cream until it starts to boil. Remove from microwave and pour over chocolate chips.
2. Cover bowl with saran wrap and let sit for 5-7 minutes. then whisk together until smooth.
3. Allow to sit for a few minutes until it just starts to thicken, then pour over the top of the cake, spreading it over the top and pushing some over the sides to create the drip.
4. Place cake in refrigerator and make the peanut butter buttercream.
5. Beat the butter until smooth, then add the peanut butter and mix until smooth and well combined.
6. Slowly add the powdered sugar and mix until smooth.
7. Add water or milk, as needed, to get the right consistency.
8. Remove cake from fridge, and pipe buttercream around the top edge of the cake and sprinkle with mini chocolate chips, if desired.