Preheat an oven to 350 degrees F (180C). Grease 3 8-inch cake pans with baker's floured spray, or grease and line pans with parchment paper.

Whisk together eggs, buttermilk, and vanilla. Add to dry ingredients and mix until no dry ingredients are visible. Scrape down the bowl and beat for another 20 seconds.

Fill the three pans evenly - I find a kitchen scale helpful for this part, and each of mine weighed out to about 550g. Bake for 30-35 min or until a toothpick inserted comes out clean. Allow cake layers to cool for 10-15 minutes on a wire cooling rack before removing from pans, and cool completely before frosting. Set in the fridge or freezer to accelerate the cooling process if desired. (This is a great time to make the frosting and ganache!)

Beat together softened cream cheese and butter; slowly add in powdered sugar alternating with milk until frosting reaches desired consistency. Add gel color, vanilla, and salt if needed and beat until well combined.

Meanwhile, make your ganache. Place chocolate chips in a heat-proof bowl. Add whipping cream and microwave on half power in 30-second intervals, stirring in between until fully melted and smooth.

Once your cakes are cool, level them (if needed/desired). This can be done with a cake leveler or a large serrated knife and a ruler. Place a smear of frosting on your cake circle (to keep the cake from sliding while you decorate it) and center your first cake layer in the center of the circle. Spread the layer with frosting, and pipe a rim around the outside. Crush or chop a few Oreo cookies, and sprinkle them over the frosting. Add a drizzle of ganache over the top – I found a squeeze bottle was the easiest way to do this! Add your next cake layer on top, and repeat the process with your remaining cake layers.

Now you're ready to crumb-coat . If you're unfamiliar with crumb-coating, it's just what it sounds like - a thin layer of frosting over the entire outside of the cake to keep crumbs out of your final layer.

Once your crumb coat has set (this takes about 5-10 minutes in the fridge), add your final layer of frosting and smooth. I like to use an offset spatula and bench scraper for this part. Once your cake is covered, place it into the freezer to set the frosting and to chill the cake in preparation for adding the ganache. (If your ganache is still liquid, set it in the fridge or freezer for a few minutes so that it will firm up enough to spread onto the cake sides!)

When your ganache has cooled to a spreadable temperature, remove your cake from the fridge and ‘smudge’ the sides with ganache with an offset spatula or a spoon. I used my bench scraper to smooth a few of the larger smudges, but kept the uneven texture of most of the smaller ones.

Transfer the rest of your frosting to a large piping bag, fitted with the tip of your choice. Alternate swirls of frosting with Oreos cookies around the top edge of the cake.

Crush a few more Oreo cookies, and sprinkle them over the top of the cake.