Line a baking sheet with parchment paper or a silicone mat. If using paper, make sure there is some overhang on two sides for easy lifting later. Set aside.
Add the dark chocolate chips to a microwave-safe bowl. Microwave for 1 minute and then stir with a spoon. Microwave for another 30 seconds, stir, and repeat once more. The chocolate should be smooth at this point, but if not continue heating in 15-second intervals and then stirring.
Spread the melted dark chocolate over the prepared baking sheet using a rubber or offset spatula to smooth it into an even layer.
Melt the white chocolate chips in a separate bowl for 1 minute. Stir with a spoon until smooth. If the chocolate is not completely melted, microwave in 15-second increments and then stir after each heating until smooth.
Drizzle the white chocolate diagonally across the dark chocolate. Then, drag a toothpick across the white chocolate in an opposite diagonal to create swirls. You can swirl as much or as little as you like, just don't completely stir the chocolate together.
Place the candy corn pieces evenly all over the chocolate.
Split the Oreos in half so that one side is bare and one has the cream filling. Using the black icing add a small dot of icing on the back of the candy eyes. Then place the eyes onto the cookie halves icing side down to "glue" on the eyes, arranging the eyes however you like. Gently press the cookies, eyes side up, into the chocolate.
Place the baking sheet into the refrigerator for 1 hour to harden.
Once the chocolate is set, use a knife or your hands to break the slab of chocolate bark into pieces. Serve immediately or chill until ready to enjoy.
Notes
This bark will keep for 2-3 weeks in the fridge or 5 days at room temperature.
I recommend storing any leftovers in an airtight container in the fridge. Putting a piece of parchment paper or waxed paper between layers of chocolate bark will help prevent them from sticking to each other.