Prepare a 9" springform pan by lining it with parchment paper and greasing it with cooking spray or your favorite cake release agent.
Prepare cake mix according to instructions but do not bake.
Pour ⅓ of the cake mix in the spring form pan, evening it out to coat the bottom.
One by one, dip one side of an Oreo cookie in the cake batter and line the springform pan in a circular pattern, starting from the outside and working your way in.
Leave a small space, around a dime size, in the middle of the pan where there are no cookies. You'll use this to check to see if the cake is done.
Pour the remaining cake batter overtop of the cookies. Spread evenly.
Bake in the oven for 50- 60 minutes, until a knife comes out clean. After the first 30 minutes, place foil overtop of the springform pan to prevent excess browning.
Cool cake completely before icing.
Decorating and ganache.
In a microwaveable safe bowl, combine 30 grams of chocolate, 30 grams of heavy cream, and 30 grams of corn syrup. Microwave on high for 60 seconds.
Stir until ganache forms. Cool until ready to use.
Remove cake from springform pan.
Ice cake with desired icing, leaving ⅓ icing unused.
Top icing with dark chocolate ganache.
Top ganache with icing you set aside, mixing it together to form a lighter colored ganache.
Decorate top of cake with additional Oreo cookies as desired.